ßăķëď Äłáşķǻñ: I have limited exposure to Vista. But what I have seen is not good. I would expect many programs to quit working once you upgrade (crossgrade? downgrade?) to Vista. I am a Software developer and several of my company's products don't work on Vista. Some of the products we interface with also don't work.
It also seems to be cumbersome to use. Our software, like most, is not "Signed" and does not have a "Trust Certificate" with it. So, Vista ALWAYS asks "Are you sure" every time we try to run something. VERY annoying after a while.
Finally, as with any Microsoft OS, I would wait until some "Service Packs" have been released to fix the expected bugs.
Summertop: I would most definitely call it a downgrade rather than an upgrade. All you get at the moment are some additional restrictions and obscure "security advantages" which are so annoying that everybody will ignore them/ turn them off after a short while. This article ("20 Things you won't like about Windows Vista" may be a good start, although I wouldn't agree on some of his statements, especially on his "OS-Ranking". It definitely shows some disadvantages from the user's viewpoint.
Anyway: I have not heard of any reason to switch to Vista except its improved look&feel (which is IMHO inferior to the look&feel of other modern OSes like MacOS or up-to-date Linux distributions) so far.