The facts here are pretty straightforward. Touchscreen keyboards tend to suck, even the one on the iPhone. Swype makes these keyboards suck less. In fact, it makes them leaps and bounds faster and easier to use for most people. The service is in beta testing right now for Android users, but those of you with iPhones are sadly out of luck.
Oops, never mind. I spoke too soon. Electronista reports that Swype has just admitted that they are working on a version of their keyboard for the iPhone. Whether this is something Apple will agree with has yet to be seen, but it's certainly a hopeful sign.