Errrmmm... mainly training and a bit of fun. I want to see whether I can handle a big jet and whether I like it or not (enough to do it for a career). I've done a lot of home-based study on the 737-400 and the A320, and I want to see whether the knowledge I have is accurate and useful, and most of all, do I have the capabilty. The main things I want to try are general handling, ILS approaches, engine outs, stall recoveries, takeoff, etc. I'm not too worried about the FMS etc, I can learn that at a later stage (well I'm in the middle of it not)
PS: Aerial don't do 737 training unfortunately, just called them. They just use a generic IFR trainer.