I'm currently using an original iPhone, which has been surprisingly okay and functional, but it's getting to the point where it won't run a lot of apps (notably At Bat) because it's got an old iOS, the battery and/or power detection is getting really unreliable and sometimes the phone just shuts down even though there's a good amount of power, and most disturbingly, stopped detecting the SIM one day in Montreal. A reboot fixed it, but it's still somewhat unsettling.
I'll appreciate the improved processing power, higher resolution display (for watching video), greater capacity and uhh, oh yeah, 3G bandwidth (although EDGE has been sufficient for me so far). I'll end up paying $5/mth more than my current data plan. Well, the data plan will actually be $5/mth cheaper (as I'm going from unlimited to 200 MB) but it doesn't come with text messages, so I'll have to pay $10/mth for that. Boo. Text messaging is such a big rip off in the US.