I am using the ATI software, but it doesnt do things like provide a dedicated task bar for 2nd monitor, short cut keys to move windows between monitors, have dedicated wallpapers and screen savers for each monitor. If there is an ATI software that does that please let me know.
Ultramon is definately the way to go. The price is a little steep though at $40US but definately has all the options you'll ever likely need. You can download it and try it out for 30 days or something like that