I think there's something to the fact that the iPhone's auto-correction is more suited to a touchscreen than the Blackberry's. I've found that while the Blackberry's spell-check is very good for people who sometimes make spelling errors, the iPhone's is much better about fixing fat-finger syndrome.
I would almost be tempted to say that the iPhone's spell-check puts more weight on where keys are located, while the Blackberry's is more of a straight dictionary search
And the OS have a propensity to leak memory so that as the day went on your usable memory level would continue to fall to the point where you had to pull the battery to reset the phone.
My Storm seems to have a feature that automatically resets the phone at random intervals. It handily solves that problem, but can be annoying when you're actually trying to do something with it.
Seriously, though, the sluggishness of the phone is a big drawback. If it could keep up with how fast I type and not randomly reset I would be very happy with it.
Lend money to a bad debtor and he will hate you.