Vista 64 is a disaster for enthusiasts - LOADS of stuff won't run because of the unsigned driver issue.
No CoreTemp (although PCWizard 2008 runs fine)
No TAT
No graphics card overclocking tools (that I have found yet)
No RAMDisk
No Virtual Machine
No SandboxIE
(the last three are hugely useful for software developers as they allow a completely decoupled development environment)
Now, I do appreciate that I can boot my machine with signed drivers switched off by using F8 during boot, but as I like to run my machines permanently 'up' they crash when Windows discovers the unsigned drivers and decides to overwrite them with 'good' code. Very definitely not stable behaviour.
I've been a Microsoft platform developer for almost 15 years now - using everything from Windows 3.1 and DOS onwards and Vista is now so difficult to develop applications for (unless you are using Microsoft's own crippled tools) that I'm genuinely considering giving up. I can appreciate that they want to kill off 3rd Party RAD tools, but the prospect of being forced to develop for .Net rather than at the assembly code level just annoys me.