Vista's main problems are that it doesn't like old hardware and it doesn't like old software. So if you are still running an essential piece of software to perform a particular task, see if it can be upgraded or replaced.
Hardware issues are not as severe though. The first thing you need to know is exactly what hardware you have in and attached to your computer. (Vista Upgrade Advisor might help) Now go visit the website of the maker of each piece on the list and do a search for Vista.
A few heroes and villains here to mention:
Haupaugge, maker of fine TV cards has committed to bring everything into support under Vista but only the newer stuff works with Media Centre. Most people who don't plug their PV into their TV won't care and will be applauding even the basic support available.
Creative Labs have simply withdrawn support for their pre-Audigy 2 sound cards. If you have an older card, expect to receive basic sound support courtesy of Microsoft and nothing else. No 5.1. No Dolby. Just "dingly" noises. Buy or own a more recnt one and you'll have some beta and/or incomplete drivers which will mostly work.
HP have simply said "no" to older hardware and provide links to shinier new devices that you should buy. So my HP PSC1215 that works perfectly under XP is not obsolete according to HP. It will print. I can onvince the GIMP to scan from it but the array of buttons on teh printer itself no longer work. Gee. Thanks HP, I'll be sure to buy another printer off you.
nVidia, maker of at least half the gaming-quality graphics cards in computers around the world didn't manage to get their drivers working with Vista and paying weekly visits to their website to get the latest driver is currently an essential activity.
