I still say XP is and always will be a legend of an OS.. It (as with most versions of Windows) took a while to perfect but once it was perfected it was, and still is in my opinion, a beastly OS.. I mean come on, you can do just about anything to it and it just keeps on tickin..
There is a time though to let good things end, and Windows XP is no exception.. I still use it everyday and probably will continue to use it on a daily basis for quite some time, but it definitely isn't my primary OS anymore..
As for Windows Vista, that to me, was more "broken user" syndrome than anything.. Many users expected to have an OS that worked just like Windows XP and that was just as fast if not faster than Windows XP out of the box... And though this SHOULD be the case with any new OS, it definitely isn't when the user is still using that 5+ yr old pc that hasn't seen a hardware upgrade since it was new and being put together..
Once equipped with a rather large amount of ram and some other minor upgrades, Windows Vista really wasn't that bad of an OS.. But to each his own..
The one thing that always got me though was when users would rush out to get the newest Windows OS and then do nothing but bash it when it wouldn't run on the aged pc or for some wouldn't even install. They then would proceed to complain and bash MS and all of it's products.. We (the forum gurus) would give them advice like, maybe you should think about getting another 512mb of ram, seeing as it is dirt cheap these days.. Or maybe you should think about upgrading a couple minor components just to get that extra boost your pc needs to be able to run this new version of Windows that you just had to have..
They would of course always answer with things like "I shouldn't have to upgrade anything on my pc just to run this product, it should come ready to work on my pc no matter how old it might be.." That was always my favorite reply to get.. A definite head shaker that one.. Oh well, enough rambling for now..
I agree that the Windows 8 beta should be very exciting to test and see flourish the way Windows 7 did.. And I'm sure we'll get a few wonderful colorful comments from those more 'enthusiastic' users..
As for the OP question, yes I will definitely be upgrading once the new Windows is released.. and definitely testing it throughout the various Beta, RC and RTM builds..