It ain't cheap though, you'll need to spend thousands on it including the mothly charges. I will not go through the package details, but you can check it out here.
So far I've tested 2 iPhone units before, one from collegemate Charlotte and another one from current classmate Yong. Also tested the Ben's iPod Touch which is quite similar to iPhone except it doesn't come with phone function.
Was impress by the functionality of the unit, but I'm not so used to typing texts via touchscreen keyboard which is quite small.
Anyway, I'll see whether I can get one unit to play around with when I went over to Japan, as I heard now SoftBank (Japan's telco) is offering iPhone at 0 yen 'til May, so I might as well signup to grab one before the promo ends. Rumours spread that possible 3rd generation iPhone might be launched in the mid of the year.
I dunno whether this rumour is true or not, but anyhow I would be happy if I were to settle with a 2nd generation iPhone.
Oh and one thing I wanna add, iPhone's sound quality is quite impressive as well, tried and kinda love it. :D