the character limit is on all phones pretty much, if you send 162 characters on my focus, it shows as one, but really counts as two messages.
cdma is really the issue... because non of the gsm devices on at&t or t-mobile make you create another message. on other platforms (blackberry), there are apps that can split it for you.
i think it has to do w/ the os and cdma vs. cdma only. there are some devices on cdma that do it automatically, i believe. i have sprint and i believe my pre splits it up. can't remember.