I have an iPhone since one year so i can help you if you need
I have a lot of apps so that depend of what you need, i have Twitterrific, Facebook, Myspace, Shazam, Liveradio, Sports.fr, France24, SoTV, Velib, RATP (Paris Metro), Premiere (Movies and theatre), Aroundme, Wapedia, IM+, Fring, Translator, Ebay, Pianist, Guitarist, XE Currency, Conversions, Lightsaber, Polarize, Yellow Pages, Taxi, etc
I have also many games like Holdem, Blackjack, Tetris, Check, Chess, Mastermind, Crash Kart, Monkey Ball, Labyrinth, Guitar Hero Tour, Midnight Pool, Let's Golf, Real Football
About the bluetooth you can only use Apple bluetooth device for the moment i know it suck.
Otherwise you don't need special tips because it's so easy to use it and it's really the best smartphone i ever used i couldn't antyhing else now !
But if you want my advice :
Save your battery i mean always turn off 3G and Wifi when you don't use it because it will ruin your battery during the day, i only turn on when i need it for use internet and after i turn off otherwise your battery will not finish the day.
Next tip use wifi if you have a hotspot near you because it's speedest and use less battery than 3G when you go on internet.
You don't need to turn on the both use only one in the same time for internet because only one connexion is needed.
Ask if you have some others questions