My first impressions after using Windows Vista extensively are somewhat positive. The only major problem that remains is that I'm completely unable to have Windows Network work between the Vista machine and another desktop with XP. However, there were other problems, one of which had to do with "limited network connectivity".
The way to solve that came up after some major Googling (major because the help in question wouldn't come up without the term 'DHCP'): Vista uses a broadcast DHCP flag that wasn't used by XP and some routers cannot handle that properly. So I appliedthe suggested registry tweaks and it started working.
In my case the default setting was DhcpConnForceBroadcastFlag set to 1 - which I removed from the registry. After that I added DhcpConnEnableBcastFlagToggle with a value 1 and the network connectivity warnings disappeared. Oh, a reboot was necessary, of course.
Weird how everything in Windows needs a reboot: I also had a printer problem which magically disappeared after a system reboot. One really hopes they'll come up with another way to sort problems in some future version of Windows...