Nigh on a decade ago
At home I began weaning myself off of IE. It took a year running IE and FF before I was using the latter more than the former. About the same time I was running Windows 9x and installed XP to multiboot. Again it took about a year before I was using XP more than 9x. I must have been running Vista/Win7 for 3 years now but still overwhelmingly use and prefer XP.
Incidentally the pathetic bug in XP whereby Common Tasks change depending (in my experience) on the no. of certain types of file, e.g. enough JPEGs in ANY folder, on ANY drive, and you find, say, System32 is now supposedly a folder for photos, with view type set to thumbnails. Or set one folder to a particular view type and you find that My Computer has changed with it; change My Computer back and the other folder changes too. Well, not only have M$ never bothered to fix this in XP, it still happens in Windows7.
I figure there is a time in every user's life when the feel for computing comes together at last, like they will never be more attuned to this technological interaction than they are at that particular time. And the OS they're using more often than not becomes the one they swear by and thereafter resist moving on from. So maybe that is, for me, XP. But while there are a handful of changes in Windows7 that I quite like, and have been prepared to put in the time and effort to familiarise myself with, much of it seems detrimental, awkward, like change solely for the sake of making a new product to sell 'Windows' all over again.
I'll be interested to know how new PC users who do their apprenticeship with Windows7 find retrospectively learning XP. Not that many will, of course.
Witness the evolution of car, aircraft, motorcycle styling over the last 100 years. There have been many turkeys, but plenty of classic designs, plenty you could almost call works of art. But now most of them are so similar they're a boring, spirit sapping waste of resources. Perhaps they are ergonomically better, but I'm as sick of silver cars as Mr Anchovy was of Chartered Accountancy! Just because it is new doesn't mean improved and it seems to me precious few of the Windows7 changes are ergonomic rather than merely cosmetic, and when they're *un*-ergonimic even eye candy is tainted with fail. Time will tell.