GPS in their iPhone? I've had a Nokia N95 with built-in GPS, as well as just about every other feature under the sun, and hardly ever used it. In fact, the only time I really did make use was when I was showing others that the phone actually had it. Yes, it was a battery hog and yes, it took forever to actually load my position, even with the software update. The iPhone's Google Maps application is fantastic and I used it as an actual turn by turn utility yesterday to find a birthday party: worked great - faster, smoother, and easier than my N95. I would much rather allow the iPhone to maintain its sleek and slim design instead of sticking a GPS chip inside.
Other additions to the unit? Just let me use disk mode, send MMS, and download necessary files (doc attachments, etc.). Honestly, I don't care about 3rd-party apps because I've had several Windows Mobile, Palm, Blackberry, and Nokia devices and I hardly ever used any 3rd-party apps whatsoever. Also, I would love to have wireless iCal sync through .Mac or Exchange calendar. Right now, I have a crazy sync song and dance: my Blackberry syncs with my Mail2web Exchange Server (amazing Exchange service and highly recommended), my MBP then syncs with my Exchange server through using Entourage when I get home, iCal and Address Book sync with Entourage, .Mac syncs with iCal and Address Book, my Mac Mini syncs with .Mac, my iPhone syncs with my Mac Mini (where all my iTunes action takes place). I know it sounds crazy but it is all rather streamlined now and it takes my a whole two minutes to go through the motions. Still, I would rather have the iPhone sync directly with .Mac or Exchange Calendar.
Other than that, I'm good for now.