Why would I change from Windows 7 to Windows 10

Here is a good article by Ed Boot which is useful in the context of this discussion. I have always valued Ed Bott's opinions. He is one of the few IT journalists that really knows his stuff. And he always presents a very balanced view.

Some first impressions of Windows 10 | ZDNet

Here are some snips that I like from what he is saying:

The decision to shrink the icons on the taskbar from 32 pixels on each side to 24 pixels feels misguided; on high-resolution screens in particular, the icons are too small to be readily identifiable. At a minimum, I'd like an option to restore those too-small buttons to their previous size. An option to scale those icons would be even more welcome.

Good riddance to the corner-based navigation that was the hallmark of Windows 8. I am not alone in hating the original navigation paradigm of Windows 8 (move the mouse to a corner and wait for something to appear). The Hot Corners feature in OS X is similarly annoying and one of the first things I disable on a new Mac.

So Windows 10 replaces the charms with a notifications pane that occupies the same general space but has more value. The customizable buttons at the bottom of the pane actually allow you to do something with a single tap, unlike the charms, which just lead to the place where you get stuff done.

Allowing the option for modern apps to run in a window, as Windows 10 does, makes a huge difference for using them in a desktop setting. The new Start menu helps, too. In fact, the whole experience of using Windows 10 on the desktop finally feels like an evolution of Windows 7 rather than a sharp left turn.
One area that still needs work is how to allow access to settings and other app commands in modern apps. The "hamburger" menu (a stack of three horizontal lines) in the title bar feels incomplete.

Ironically, given how much work went into building Windows 8 as a touch-first, tablet-oriented experience, Windows 10 feels most incomplete in that environment. Pendulums work that way.
With most of the desktop work out of the way, it's time for a little more attention to those touchscreen devices over the last few months of this effort.

That's an interesting thread to read! Here's my 2 cents ...

Indeed, as a regular user, I don't see much new functionality in 10 (as I did not see in 8) as compared to 7. That's why I work in 7 and have 10 as a separate installation which I use simply to keep up with the new developments and I'm not really excited at what I see.

I do not understand the argument "modern apps are the future, so just get on with the program". For my work right now I am not aware of any modern app that does something better than my desktop programs. Even if there are modern versions of those programs, I don't see any advantages in choosing them over the desktop versions. I surely won't do it simply because "it's the future".

I also do not understand the argument "five years from now there will be new hardware which will not be supported in 7". Of course there will be. When such hardware will appear and when/if I will need that hardware, I will get the appropriate software to use it. What does it have to do with the question of whether one should/would want to "upgrade" their existing machines from 7 to 10?

I also don't see the problem with the support cycle. It seems to me that 7 is not being dropped for the time being. It might be in 2020, but that's so far in the future that I certainly won't base any decisions I make this year on what might (or even will) happen in 2020.

Finally, I do not understand the comparison with cars and/or other material things. Material things tend to get "used", "old", whatever words you want to use. Shiny surfaces get scratched and dull, the upholstery gets worn off and smelly, the mechanical parts get broken and need to be replaced one after another, the list goes on. Yes some people like to run their cars into the ground and some people get new cars every other year. What does this have to do with the OS? In my mind, nothing at all. Your software looks as good as your monitor/graphics card allows and that does not change over time (unless you hardware breaks down). You may get bored with it, yes, but the OS will not give you that "used" feeling as an old smelly car with worn out seats.

In my opinion, there are basic OS functions and then there are additional bells and whistles.

Basic functions - file management, tasks management, tasks automation, etc. - have been pretty much perfected long time ago. Most of OSs since Win2000 can do that, it's the question of doing it faster and maybe having a bit more options. I have always had the impression that 8 was a tad faster than 7 in this department, but the difference was not essential. I'm not sure about 10.

Now, extra stuff - web browser, media features, cloud integration - that's another story altogether. Of course you expect to get more exciting features bundled with the new OS. So far with 10 this actually did not happen in my opinion, but it is indeed a preview build that keeps changing with every build and that change is not always progressive.

So now what's left is the UI and that seems to be the center of most discussions. Well, this is of course a matter of subjective preference. I for one don't like the UI. There are plenty of issues, but it's pointless to list them since, like I said, it's subjective. Others may actually like them.

So at the end of the day my strategy is wait and see. I will keep updating my installation of 10 in order to see what's going on, but for now my work will remain in 7. Will I "upgrade" later this year? I don't know. To me "upgrade" means getting something that works better than what I have. If that's the case with the final version of 10, then maybe I will.

I think one of the main purposes of Windows 8 and 10 is to move applications to a more compartmentalizes/system-agnostic form, which will allow Microsoft to rebuild the OS from scratch without dropping compatibility. Windows 8 and 10 are pretty speedy, but if it used a RTOS like Blackberry's QNX then there will be a night and day difference in performance and security. The old XP kernel predated the internet age and it's security requirements, and the NT kernel was created when we were still figuring out best security methods (and the hardware was weak enough to restrict use from using the best practices). I think one of the main reasons of 10 is to transition to the Modern development language, to reduce the number of broken applications when Microsoft starts rebuilding the OS from scratch and dropping legacy compatibility code from the core of the system.

Plus: you do have to be careful when using the "if it ain't broke don't fix it" mantra, ESPECIALLY when Microsoft is going to make the new OS free to upgrade to. That mantra is why many people stick to XP despite being told of better OSs, and although they may be correct in saying they can mitigate XP's major problems it's still not that great for everyone.

Some peoples moto is if it ain't broke don't fix it
Same is said about upgrades :)

I've been running windows 8 and now 8.1 since day one but had to install windows 7 on a NUC because some legacy software I use unfortunately runs better (less CPU usage) in windows 7. The angst level when seeing Aero again, damn! I'd update only for the visuals.