Onya Matt. It's the single best bit of personal electronic gear I've ever owned. The knockers don't know how good they are, and would probably offer an opinion on them before they'd used one for a while. Simply brilliant. I've only ever bought apps from the iTunes AppStore. There are thousands, and it's all very well integrated. Updates are automatic too.
I have NOT succumbed to jailbreaking the phone - because I don't think that the average user would ever need to. If you're a geek who really just HAS to go around the gate house because you can and bypass the guard - then fine. Apple-sanctioned is the way to go - everything is supported then.
My apps (apart from the standard suite that come with the phone):
Angle (Inclinometer)
Treasure Island (Audio Book)
Australian Oxford Dictionary
BeatMaker (Synthesizer)
Covert (Unit & Currency converter)
Darkness (Moon, Sun ephemeris)
Red LED Digital Clock
Documents To Go (Opens office docs)
Domain.com.au (House finder)
EAT (Sydney restaurant finder)
Currency (another currency converter)
Free WiFi Finder
Google Earth
Google Mobile App
HDR Camera (photo manipulation)
iEphemeris Pro
iSSH/VNC (terminal & remote console)
The Curious Case of Benjamin Button (eBook)
Linux Cheat Sheet
Moon Map Pro
MotionX GPS
Myst (The game - brilliant on iPhone)
Noise.io (Synthesizer - brilliant)
Oz Weather
Perpetuum (Moon phases)
Pocket Data SQL (mySQL database applications)
Roget's Thesaurus II
Shazam (Music analyser - finds music by hearing it)
Shopping List Lite
SkyVoyager (my favourite planetarium)
SQLschool (SQL reference)
StarWalk (another good planetarium for public nights)
SkMapPro (sophisticated planetarium, but not my fave)
Sygic Mobile maps Australia (turn by turn TomTom/Navman equivalent)
The Time Machine (eBook)
TripView Sydney (train/bus/ferry timetables and trip builder)
UrbanSpoon (Australian restaurant finder)
X-Plane Airliner (great flight sim)
12C RPN Business Calc (replica of HP12C RPN calculator)
670 songs
Have fun Matt