I have the PST and I love it! I think it's perfect for my needs, but I don't usually carry too much stuff. Mine normally holds the following (just to give you an idea of how much it can carry): Medium-sized wallet, small make-up bag, journal, pocket agenda, Nokia N95 phone, credit card holder, memo pad, small water bottle, and Chanel sunglasses with the case. HTH!
Edit: I just read your post about getting the GST...congrats!