Windows XP will be my last
I haven't tried Windows 7... I hear good things about it... but I use Windows so rarely, I see no viable reason to update. (Note I say up*date*... updates are not necessary upgrades... e.g. XP->Vista.)
My main workhorse is a Lemote Yeeloong netbook computer -- sporting a 64-bit RISC CPU (ST Micro Loongson 2F to be exact) -- and is designed to run Linux. The machine I use at work is a P4-class laptop running Windows XP ... with all the visual effects turned off and the classic UI enabled.
My work involves embedded software development, these days on ARM (Luminary Micro Stellaris), but also MCS51, MSP430 and TMS320C2000. The latter two require software that only runs on Windows (to my knowledge). The former two are easily programmed using free software. (I have hand-compiled a version of CodeSourcery ARM-EABI for Stellaris, for MCS51 I use SDCC.)
I find KDE's desktop allows me to get a lot more done than anything Microsoft has offered. It's got a little bit of eye-candy... if you want it, you can enable it, but it's optional. The big feature for me is the ability to customise the keystrokes. I can for instance, move windows around, switch desktops, move windows between desktops, close, maximise and minimise windows ... etc... all without touching the mouse. FVWM is also good for this. I'm sorry, I don't go for this "standardisation" thing necessarily... it's *my* computer, I'll have it work the way I want, the way that suits *me*.
Microsoft didn't offer this in Windows 3.1, and still doesn't offer it in Vista... don't know if Windows 7 offers it, but it's too late for them to start now.
Windows 2000 & Windows ME both changed the way networking operated with the shift from the classical "Network Neighbourhood" system in Windows 95/98 (which was a big improvement from the mess of Windows 3.1), to the "My Network Places" mess in later releases.
The former was good because you could go to one place, and see all your local systems... if you knew where to find something, you could get there quickly. Now, one must go "My Network Places" -> "Entire Network" -> "Microsoft Windows Network" -> "Workgroup"... to bring up the same list (meaning you must know the name of your workgroup). If you didn't know where something was kept, neither interface is particularly useful IMO.
An operating system should sit in the background and keep out of the user's way. Microsoft and Apple both insist that their OSes are the centrepiece of computing -- it's not... they're really just a collection of hardware access libraries that allow an application to get about its business.
Linux does this nicely... This is by no means the only option, just the one I've chosen for my needs. At the end of the day, once the operating system is configured for the hardware in use, the OS fades into the background and the user focusses on the work at hand.
It should not matter what the underlying software and hardware is; so long as the work needed can be achieved with a minimum of fuss. This is going to mandate a different hardware/software stack for different people -- that's a fact of life. I can (and do) get to and from work (about a 160km round trip) purely by public transport -- but this is not an option for someone who may need to take a large amount of items with them, or need to travel at odd hours. Just as much as we use different modes of transport to suit our needs, we will also use different computing solutions to suit our needs.
This will ultimately require a move to open and royalty-free standards ... we've seen the benefits of this with the Internet and TCP/IP... now we need to move higher up the stack and target our file formats. The sooner we move to truly open standards, the sooner the OS debate will fade into the background, and the sooner we can get on with what we want to do, rather than battle a system that really doesn't suit us.