I use 2007, as I am testing it for our company. It is a major change to the interface, but once you get used to the ribbon, it's pretty nice. It's a major change for us because we have been using 2000 up until now. Getting 500+ people onto a new office suite is going to be tons of fun!
Would I recommend it for the cost? It depends on what you need it for. If you need more lines in excel, then it is your new best friend. For daily activity... stay on 2k3 or OO.