sure there're a few iphones around but Palms really not taking them on so much as the widely entrenched Windows Mobile versions, which sadly DON'T have this. Seriously, how f'in hard can it be to implement?
Anyway, I run a program called PocketCM thats a very iPhoney interface with finger scrolling and threaded texts and such.
Thats a VERY effective ad from a consumer appeal standpoint however. The threaded SMS gripe is a pretty big one among Windows Moble users.