STL's terminals, with the exception of the East Terminal, need major work. There needs to me more room, more concessions, and something needs to be done about all of that brown paint! The city of St Louis (who owns the airport) needs to get it's act in gear and do something to improve the facility. I figure they should start on the A concourse and get the occupants there (basically any one other than TWA, TWE, SWA or charters) to chip in and modernize the gate area. By they time that is done maybe TWA will be in better shape and they can update the B, C, and D concourses as well.
From a service stand point, STL is a good airport. Despite the fact that the entire airport has 8 baggage carousels (2 of which are in the east terminal) I have never waited that long for my luggage. Since you will be on AA you should be arriving at one of three AA gates A10, A12, or A14 (I think those are AA's gates, although one is shared with Skyways). From there it isn't that long a walk to the baggage claim, atleast, short compared to walking from gate C-36s to baggage claim M1! All of the exits are numbered and most rental car companies/hotels have adds that tell you which exit to go out of to get to their shuttle busses. The check in area isn't very fancy, but it is bright, well lit and basically one big open space with counters on the two long walls.
I gotta agree with Acvitale though, TWA is great, but STL sucks! Enjoy your trip to STL!