XP in the main, but I do recognise that I am rather out of date and accept that there's going to be some creeping incompatibility problems when running what is effectively an 11 year old OS with a few security and UI tweak patches.
(Compare previous editions: it would be the same as using Win98 until 3 years ago, 3.1 until 2003, and original MacOS/Workbench/GEM until about 1995/96...)
It's mostly because my main PC is a laptop I bought in 2006 (before Vista was even a thing, and buying something with XP SP2 on it felt fairly advanced coming from home/family/workplace experience of using 98, ME and 2000), and having long since upgraded it to the absolute limit, I'm now trying to work up the budget to replace it, possibly at the point it hits exactly 7 years old. Other life things like my car ... bike ... flat going wrong in various ways have kind of taken precedence instead, though.
I mulled over upgrading the machine to 7, but... given the age of the hardware, the gradually diminishing effective performance level (it's finally sliding from "acceptable" to "a little sluggish" for everyday use, as it has decent-for-2006 specs, but game performance disappeared long ago) and the likely issues with finding suitable drivers - combined with the sheer lack of benefit that I've been able to determine in most post-upgrade cases I've seen - I decided not to bother.
At work I'm about the last person still using it as there hasn't been any opportunity to re-image my desk PC ... and the Win7 image has some bugs I'm waiting for everyone else to get done with reporting and ironing out before I finally make the leap. It works fine as it is, after all.
(Will definitely take 7 over 8 for now, mind)
Most people I know are on 7 by now. Not going to complain about being left behind when I am so pointedly out of date.
Down under my desk, btw, is an olllllllllllllllld laptop (strictly AC power only by this point) with Win95 Lite and Office 97 installed on a 2GB CF card in place of its HDD, which I use for distraction-free word processing and the like when everything gets a bit too much. Or at least I would, if I hadn't been so stupid as to leave the "solitaire" box ticked when installing...
(It still does everything it ever needed to, and ever will need to do. Therefore, it's still a useful tool. Same as the 2006 machine will be once it's replaced - though it's kind of beaten up and has a few broken bits, it will be retained for its exceptional compatibility with software and (Cardbus/USB) hardware produced in the 1995 thru 2010 period...)
