Unless you absolutly need Windows Vista, I would personally recommand avoiding it for the time being. It's incompatible with a lot of hardware, and also it's just not necessary if you are currently running Windows XP or Windows 2000. What are your thoughts on this subject matter?
Not necessary is rather a subjective view, more objectively it does address a lot of OS level security issues and from that perspective it's a valid upgrade to take.
Personally, if you are running mission critical systems at whatever level, I would wait until the release of SP1 so that the bugs are ironed out.
But my test machine running Vista has had no problems with hardware compatibility, has been stable, and I actually rather like the Aero interface it has to be said.
Again, I guess it really depends on what machine you have and what you are going to be doing with it.
Since I just built a new computer, and would be stuck buying another liscence of XP anyways, I went with Vista. I've enjoyed the experience and have had no hardware related issues.
I have however had tons of learning issues that have caused me to spend a lot of time just tyring to perform what I would deem simple tasks... Thats pain that I am going to have to go through now or later. Either way, it has to happen eventually.
As for compatability on software, I've found it is hit or miss. In retrospect I am either going to have to shell out some hard cash on updated software, or install another HD that I can put XP on and dual boot. The primary focus of my machine is video editing and 3d design. I have already found that Adobe Encore 1.5 will not run in Vista ever (pay $200 for an upgrade) and neither will my 3dstudio max 5 (pay like $2,000 to upgrade to vista capable vrs. 9)
So yeah, I'm not really happy about this, but its not vista's fault per se, each of the packages listed here failed to install because during the installation process they detect what OS you are running, compare it to some list or something and if they don't like it they fail without giving it a chance, so even if I wait until service pack 1, 2, or 3... unless they make some sort of super-vista-xp-software-100%-garanteed-compatability-installation-mode then I will be stuck shelling out more money somewhere. Either for updated programs, or for another HD and an XP liscence. :(
All that being said, I've had a rather enjoyable and crash free existance with it. The minor bugs I've ran into haven't been too bad for someone who knows how a computer actually functions and can troubleshoot it... But I feel sorry for these people just going to walmart or dell and buying a computer for the first time. Some of my support customers (The type that click block on their firewalls when it tells them ie.exe wants to access the internet and call me up to ask if we are having an outage) are in for a rough ride, and good vista tech support will take time to spread.