Going to take the plunge and upgrade to 3.5, as well as vista business and 8gb ram. Looking for opinions on most stable version of 3.5 and above to install.

thanks in advance.

Sorry, no real answer to your question, just a remark: if you are switching to Vista and 8GB, consider replacing your system drive with a VelociRaptor (10k rpm) drive. I just did that, and noticed that the whole system gets more responsive (opening folders, launching application, opening/closing/saving bins). It's not outrageously faster, but faster nonetheless.