good news and bad news
Yes, a lot of Vista features rip off OS X, but what else is new? Anyone remember Windows 3.xx? Right. For those who don't... Macs were way ahead in GUI design and general ease of use at that point (early-mid 90's). It was sort of like OSX vs XP now. So what happened? Windows 95 happened, that's what.
AND IT WAS A DISASTER FOR APPLE - IT KILLED APPLE!
When Windows 95 came out, everybody screamed "MS ripped off Apple!" I think there was even a lawsuit going on (by Apple I think, can't remember exactly, Apple accusing MS of stealing their GUI design), which Apple eventually lost. Anyhow, it was true, MS did rip off Apple in Windows 95. Windows 95 came closer to being usable, and closer to the Apple design - even though it wasn't as polished, integrated and "native" as Mac... I remember Apple making fun of Windows features by running ads to the effect that "oh yeah, about time, we've had it since 84, welcome to the fold, Windows". In any case pundits claimed that
finally with Windows 95, MS got a desktop with feature parity to Apple, and that Apple's big advantage disappeared... well, it wasn't strictly true - it was only surface parity, and underneath, Windows sucked compared to Macs, and Macs were still ahead, though by a smaller distance.
In any case, unfortunately, the predictions came true - Apple was killed... folks saw no reason to hold back. Apple had customers for their more expensive product, because it was blindingly, demonstrably head and shoulders above what MS had to offer. And so, Apple had decent market share. But with Windows 95, even though it still was not as good as Macs of the day, folks figured "good enough feature parity" and saw no reason to shell out more for Apple computers. And that was a deathknell for Apple. Market share immediately started sliding (of course, there were additional reasons, including many missteps by Apple). Apple has never recovered.
Tragically, Apple share fell so far, that even with the introduction of OS X, and with Panther and Tiger it was clearly ahead of XP, Apple fell too far down in market share to recover.
And now, we'll have Vista. Pundits will scream "feature parity with OS X", and even though it won't be strictly true (the underlying guts will still be POS MS, versus the unixy goodness of OS X), it'll be enough for Joe User 95% of the market. Yes, 10.5 will move ahead again, but the damage will be done. The distance between 10.5 and Vista will be too small for the average user to care about - and smaller than between the current Tiger and XP. That's not good for Apple.
The good news is that the market is a bit more sophisticated and as a result, the niche of Apple buyers should still be there. You won't see too many defections. But the dreams of 30% desktope marketshare will be likely dashed. Also, likely and hopefully, Apple will continue to lead with hardware design... that is definitely a factor. I'd rather work with my good looking iBook, than any laptop in the PC world - I'm sure I'm in a minority, but I'm not alone
All I can say, Jobs and team better pull out all the stops. Make spotlight way better than it is now, because the equivalent in Vista is going to beat the pants off Tiger spotlight (there was a nice article in Anandtech about this a few months ago, and the compromises Apple did to get spotlight out the door). 10.5 must be as big a leap forward as possible to maintain some sort of marketshare.