Probably not half bad
First off, how many morons jump right to "MS Can't count" comments without reading the 38 already posted? We must be on the Internet here or something for that sort of behaviour. That goes along with posting complaints on subjects of which you are ignorant, like the previously pointed out fact that 95/98/ME are counted seperately.
And then there are the comments about how much Windows7 will blow ass, since it'll be like Vista. I'm no Windows fan (I use it because they require me to at work, other than that it's Slackware or nothing,) but I have reasonable expectations for Win7. That's because I've used Win2008 a bit, and it was quite a slick OS, even running on my 2.5 year old desktop. From what I've heard, Win7 is supposed to be more closely related to 2008 rather than Vista, which makes sense, since 2008 is just an incremental improvement upon Vista with some server software thrown in.
Honestly 2008 ran faster on my desktop than XP did, and it's just about the first Windows release that I've ever enjoyed - I tend to keep the older version as long as I can to avoid the performance hit on the new version. And for reference I wasn't running Aero or anything to waste cpu/gpu power needlessly.
So Windows 7 could be decent. And they shouldn't have all that much development to do for it on top of what they've already done for 2008, so it might not even take them that long. There's always the great chance that MS will screw it up royally though.