Good luck. See you back here in a month or so, after you've tried using it as your day-to-day phone. 🙂
[I'm speaking as someone who tried and failed to do just that.]
As for an iPhone replacement, I'd recommend the Nokia E71. It's 3G (3.5G actually), is much thinner and lighter than the iPhone, has awesome battery life, supports three or four different types of "push" e-mail (including IMAP IDLE), uses microSD for expandable storage, supports H.264 and AAC, and has an actual keyboard with a predictive autocorrect that doesn't make me loathe the phone. App installation isn't as integrated of a process, but it's pretty damn easy. I can sync it wirelessly via Bluetooth, or tether it via Bluetooth or USB (both supported, manufacturer-sanctioned features.)
Oh, and you can buy a one unlocked direct from Nokia for half the cost of a PAYG iPhone 3G.
I'll write up a detailed review/comparison some time, but suffice it to say that if you can deal with a non-Apple device and a slightly smaller screen, the Nokia E71 beats the iPhone pretty solidly in a lot of areas.