[rant]
I know i come over as a total bore harping on, but aren't you describing how to step by step remove Modern UI from the OS? If so, what is the point on installing the OS in the first place? It's marginally better in some functional area's but nothing major.
I am seriously curious what drives people. Is it because it's 'new'. Because it's the 'future'? Is it the same thing that makes Applers buy the latest Apple whatever?
Maybe it's my age and i am really becoming to old for this, but in my vision stuff is there to be used not to 'make you one of the gang'. As now, i see everyone suddenly with these huge headphones instead of earphones. How happy i was to be rid of those cumbersome things 20 years ago. Today i wanted to buy another pair of earphones, hardly to be found.
Consumerism has become a goal in itself, as exemplified by this Windows 8.
Tablets are gadgets all said and done. They are handy for certain tasks but a disaster for most normal uses. Fumbly, big to lug around for what you can do with them. So a keyboard gets added so is becomes somewhat usable, turning it into a clumsy expensive notebook with a buttugly Modern UI interface.
If that's not bad enough, now it's foisted on everyone's desktop and even the most avid proponents post how to deactivate that UI step by step as workaround get discovered to do so.
And no single user of the mess asks himself: why in hell am i doing this? Why do i install a new OS and then remove everything that makes it different?
Jezus, i'm getting old 
[/rant]
Sorry for the short novel... I am concise, but I am by no means brief unless I have to be... and here, I don't! ;)
I agree with you to some extent, but not entirely.
For starters, people are always trying to upgrade to the new whatever. Somebody mentioned that this is the youngsters and that they are wasting time, money, and effort (paraphrased because I don't want to bother embedding the quote in here right now) but this simply is not the case. I obviously don't know what anybody's experience, work or otherwise, is, but I can tell you that this need to upgrade to the latest versions extends all the way out to the oldest of users, especially at the professional level. At my previous job we did support for our long time customers for free and offered it bundled with the systems we integrated for all customers. The most common problem that required support was these IT professionals upgrading to the latest version of whatever flavour of Linux their servers were running and it totally breaking everything. Obviously the first question we would ask them is why they upgraded, what did they need from the new version that the old version didn't provide them. The most common answer:
"Uhh.... It was released... and it's newer?"
We live in a society where the mentality is that anything that is newer must be better and that we need it even though we don't know why we need it (or, usually, don't need it). This is most new in electronics where even a year old is usually considered 'ancient' anymore because the product lifecycle keeps getting shorter and shorter so that companies can release newer versions faster and, thus, yield higher revenues. The truth is that most of these don't offer significant benefits and even those that do are usually not required by the user in the first place. Android was a good example of this for a while and the media grabbed onto it and canvased the internet with it for quite a while. The update cycle hasn't really improved for Android devices and most are still running outdated versions of the OS and yet I hardly see anything about it any longer. A few people got it in their mind that because a newer version was released by Google that they must have it and that because it wasn't available for their phone (though they couldn't pinpoint the reason why in almost 100% of cases) that somebody was cheating them and they were somehow suffering greatly. Never mind that the only app they used was Meebo. This is a real example of a fellow student of mine when I was still in college... he only used the Meebo IM chat, made phone calls, and sent text messages... but he was livid that he couldn't upgrade from 2.1 to 2.2. The worst part, he was a computer science major with an emphasis on embedded devices and now works as a consultant
Of course some of the upgrades did provide some benefits, but the truth is that most of the improvements were things that the average user who was complaining about it would never use and even the performance benefits were so minimal that they provided no real benefit at all, just a perceived one.
So, to sum up the long bit there, I agree that we live in a society where everyone feels this crazy need to upgrade regardless of what benefit it provides them.
At this early level, most PC users will see absolutely no benefit (or possibly even a hindrance that they have to try to mitigate by removing the additional features that are only getting in their way) from upgrading. However, there is actual reason to eventually upgrade as Windows 7 will not receive the same support that Windows 8 will. This wasn't handled in quite the same way as things were with XP that continued to receive support for a long time because Vista struggled so much. The transition between Windows 7 and Windows 8 should be much smoother though as, like you noted, the changes really aren't that significant and are mostly just cosmetic with numerous workarounds even if it doesn't suit your needs. This will most notably be seen for gamers, though, and not a real issue of productivity. The same thing is what drive me to have a Windows Vista and a Windows XP drive early on. If I remember right, it was DirectX10 that wasn't supported on Windows XP and was on Windows Vista and one of the initial big selling points aimed at gamers. I played several games that looked and performed better under Windows Vista (back when I still had time to play video games
) but I hated the operating system itself because it was so unstable for me, especially in those early days of its initial release. I see the same thing happening for future versions of DirectX and other technologies -- included with Windows 8 but not Windows 7. Why? Because, as you pointed out, there isn't really any need for users to upgrade, so they have to create that need with a carrot. If you want these features, you have to upgrade.
As for tablets, I have to disagree. Like everything in technology (and, well, really life), there are always trade-off's with everything. The same thing applies for the difference between PC's and laptops. Every product offered has its advantages and disadvantages. I got my first table for free at Google IO 2011, the Samsung Galaxy Tab 10.1. At that time I didn't really see the value in tablets for the most part, either, and was in a position where I was happy to be given one for free for attending the conference, but wouldn't have otherwise bought one myself. Truthfully, Android hasn't released a tablet that I would buy yet because the incentive just isn't there for the prices asked (unless you buy one of the, in my opinion, "junky" off brand models). But, having been given the Galaxy Tab 10.1 for free, I have actually gotten significant use out of it. For me, I mostly use it around the house to consume, but I do take it around with me on occasion. I'm not really sure what you mean about them being "bulky" other than maybe your qualification for bulky is that it won't fit in your pocket (though, the 7" tabs will fit in some of my back pockets or side pockets if wearing a pair of cargos). Are tablets PC replacements? For many who only use their computer to consume media and to read/send emails, it very well could be. For myself? Not a chance. As for them being clumsy, I presume you are referring to interacting with content on them, notably how large of a pointer you use (your finger). I can somewhat give you this one. A finger is definitely not as precise as a mouse where you have single pixel precision with ease. I would argue, however, that most consumer applications don't require that precision and that with minimal practice the touch interface (if the UI is designed properly, which is one of the reasons why Microsoft did what they did with Windows 8 and where it really shines, touch devices) is more than suitable.
Personally, I'm still going to continue running Windows 7 and various flavours of Linux in my home. But, to each their own.
