Many issues such as the mentioned speed issues, will be address in SP1. That should be available early next year. Which from the reviews I have read of the Beta SP1 are true. Faster starting, copying, etc.
The requesters are there for security to basically make the user aware of the actions they have initiated, say in an program install. Doesn't bother me. I was using teatimer that comes with Spybot Search & Destroy to monitor registry changes. It prompts you for each registry change. I just didn't like the sneaky {bleep} that try to silently install.
I'm running Vista Ultimate on an AMD 5600+, 2 GB 800MHz memory, M2N32-SLI Deluxe motherboard and a HIS Radeon 2600XT ICEQ graphics card. Vista runs quite nice. It feels like a robust version of XP with a SP2 like service pack added on. It doesn't fall down and BSOD like XP. Recovers nicely and is better with program errors. Even tries to find solutions to the problems.
Really it is not a run out and get upgrade with everything that MS cut out of the features list. You'll get it with a new computer. Try it for a few weeks. The only issues I've had are not being able to use 10 year old software or hardware.
Oh, and you can turn a number of features off. You don't have to use the Aero theme, or the User Account Control (which will keep the permission requesters from poping up)
Basically, MS listened and put a bit of security in to Vista.
P.S. I'm running the 64 bit version.