I went with Home Premium... Professional is supposed to be more for businesses, and Ultimate has everything... I really see no need for Professional or Ultimate myself as I will not use everything it has to offer.
I agree with the Vista comment, and I will even go so far as to say Vista itself is and was a joke. I refuse to use it for my everyday activities, for that I have XP and Ubuntu... but once Windows 7 is out I am planning to clear off my system, reset the partitions to full drives and only have Windows 7 and Ubuntu 9.04.
I do not know if it will accept the beta Windows 7 as an upgrade option, but I hope they still allow the Vista upgrade "bug" process to work (install but do not enter CD key, reboot into the OS, start upgrade install process from disc again and use the key)