iPhone has good and bad points. My good mate has one, and went from a N95 to a iPhone.
Good:
Touch screen
Huge amount of applications available
Fast response times to everything
Large amount of space
iTunes built in
Bad:
Applications can be expensive
Screen and back cover gets covered in fingerprints
iTunes is the only program you can import music to your phone
Horrible camera
Speakers on the bottom of the phone
Hard to get custom ringtones working
No bluetooth
No MMS
On screen keyboard
My mate has dropped his phone a few times, and it hasn't stuffed up yet. They seem to be pretty hardy phones. The screen doesn't scratch easily, either.
Apparently there's a certain version of firmware that supports MMS? You might have to search around for it.
They're great phones, but it all depends on what you want to use it for. I don't think they are really a decent business phone for, say, checking your e-mails, because from memory, the e-mail program isn't a Pull-type (automatically downloads emails as they come in, rather than opening up the application each time to then download e-mails).
If you SMS alot, you'll have the Qwerty touch keyboard. The keys are very cramped, and it's hard to type quickly on it. Expect alot of spelling mistakes!
Voice quality, it isn't fantastic. Sometimes it's quite hard to hear my mate on this phone!
But application-wise, there's a huge amount available but be prepared to pay for 90% of them!! They range from $1 to about $20 and can all be purchased/downloaded via the phone.
That's about all I know of it! I've had a decent play with it quite a few times, and it's great with the touch screen, but don't know if I could use it full time. Have you seen that new Samsung phone with the Windows Mobile software on it? That's touch screen but with ALOT more features.
Edit: Oh, and forgot to mention... if you're going on a plan, make sure you get a large internet cap on it. My mate had 300mb a month and he went over it in a few days of just internet surfing, and got charged huge amounts for every mb after! The iPhones use alot of bandwidth!!