Most of Vista's problems spring from incompatibility with hardware drivers and basic machine performance vs. a user's knowledge.
Once hardware manufactures learn how to write a decent driver for Vista, then people will stop having as many problems. This is once again Microsoft's fault for brining out a new OS (yes, sarcasm).
I think the other big problem is users getting systems with Vista that aren't meant to run Vista with a basic setup and require some OS tweaking before they become compatible, with the problem of the user not knowing how to change settings or what settings to change in the first place.
If you don't have a good enough graphics card, turn Aero off. Pretty effects will not work with budget video cards until budget video cards are 256mb ddr3 AGP or PCI-express cards.
Memory. Once again, trying to buy a computer with 512mb of ram and running Vista on it will not be a rewarding experience.
Processor. People running p4's with Vista will have a machine that runs slower. period. I have a 2.0 c2d laptop and a 3.0ghz p4 desktop. The laptop runs much smoother with Vista, has the same hard drive speed and memory. There are people out there that are probably trying to put Vista onto old P4's and wondering why it's crawling. Eventually technology will catch up where the cheapest bargain PC has a 2.0 c2d or greater in it.
Compataiblity of programs. Some people are trying to run programs and having problems with them. I find for the majority of programs that won't run right or seem buggy after a clean install require you to run them as admin(because the way they access files conflicts with the way Vista's security is) and/or change compatibility options to run under Win XP SP2 mode.
This will eventually become irrelevant as technology catches up and a $200 PC includes a c2d chip, 1gb of ram, and a 128mb gpu that actually is worth. It's inevitable. At least Microsoft didn't release an OS that is going to be outdated by hardware in a year. They could have made Vista compatible with everything on the market now and so that it runs with all feature on 512ram, an old processor, and integrated graphics, but then people would be 2 years down the road because they're stuck with an out of date OS.