The blued, rental gun? That's been the factory Colt grip safety for over ten years. Most people don't like them. I've found them to be pretty comfortable, but prefer just about any other, in terms of fit and appearance.
Yeah, I'm not particularly fond of the grip safety on the enhanced models either, but it's not too bad and easy to get used to. The main thing I dislike about the enhanced models is the undercut below the triggerguard. I find that the "squared" feel to it can really become uncomfortable after a while of shooting heavy loads. Here's a pic of my enhanced GC, which seems to be the same as the one mentioned at the rental place.
The "enhanced" Gold Cups come with the commander style hammer, ducktail grip safety, and the trigger guard undercut. If yours look like mine, then it's the enhanced version. The pre-enhanced models have the standard spur hammer, grip safety, and no undercut below the triggerguard (which is what I prefer).
Wow, I know some people don't like the looks of the undercut trigger guard, but I haven't heard someone dislike the performance of them. I actually prefer the undercut. I'm having Colt do one on a NRM as we speak.