I always use correct capitalization and punctuation when I text (But not while driving anymore!). And like you guys, I thought I was the only one who did.
And now for the obligatory on-topic comment: I don't have an iPhone (yet --- holding out for a 32 GB), but I think copy & paste would be extremely useful.
I also think a legit, navigable filesystem to share files between apps would be useful, but that's for another time.