I dunno, I think like when XP first came out, you can find some really arcane power user stuff that Vista might have issues with, but most people, including myself, will never encounter those situations.
I think it fundamentally comes down to compatibility. You can have an OS with limited compatibility but good support and as a result high utility. Or you can have an OS that attempts broad compatibility and as a result of THAT, good utility. Unfortunately support for a high compatibility OS is a much larger job, and there's also the fact that an OS that is used by more people, will have more people trying to find ways to compromise it at the expense of others (ie. Hackers).
I dont think Vista is perfect. If there WAS a perfect OS it'd be a pretty quiet market.