Cmax, I'm a newbie, and was struggling with this very question, but in my case, this is for my first purchase, since I have no other guns in my collection.
Over the past week, I joined the local club, have rented almost a dozen guns, and have put hundreds of rounds (and dollars!
) through many weapons, both in .45 and 9mm, including HK, Baretta, Glock, Kimber, Colt, and Sig.
There are a LOT of really great choices out there, but in the end, I decided to order the Kimber Custom Eclipse II, since the 1911 just fit me well, I shot it as well as a 9mm, and because it's a classic design, that has endured the test of time for a reason.
Have a look at one (if you can find it...) and you'll see what I mean. Drop dead gorgeous. As pretty as they come, it's a .45ACP, and it's a Kimber. It has a lot of things going for it.
Take a look at my post here, since it might give you some ideas for 1911's, if you decide to go that route.
http://www.thefiringline.com/forums/showthread.php?s=&threadid=85445