"Best" is a personal thing. I like Go and ADW. I find myself using Go most of the time, just because I've been using it almost since I first got the phone.
GO Launcher EX is a great all around Launcher but it uses alot of memory. I ran it for about a week and watched how my phone acted. Started getting a little laggy but not too much to cause a stir. I dont run GO anymore cause it's not a smooth launcher for my phone. I have the X2 and with it's specs you would think GO wouldnt lag at all. Maybe I didn't tweak it right for my X2. I am reinstalling it later on and going to play around with it. I really like GO.