I picked up the .45 cal STI a few weeks ago, and after putting a few hundred rounds through it, I can say that I am QUITE satisfied. So much so, a 9mm STI is not too far into the future for me.
I considered the .45 Kimber, but for the money, I figured that the STI was a much better buy and it came with MUCH support from match shooters that I know.
As for the DE, I have shot the .50 cal DE. It's an impressive thump. I just don't think I could get used to the aching wrist and elbow for 2 days after every trip to the range. If I ever get a DE, it'll be the .44 cal model. Deadly accurate, cheaper ammo, more pleasurable to shoot and other than providing a slightly smaller hole, every bit as scary to the guy at the at the wrong end of the barrel. AND, I already have a .44 mag revolver, so it'd make loading a little simpler, not having to buy another set of dies.