I've used my N900 without touch vibration for 2 weeks, a while ago, I didn't notice any accuracy improvements (didn't check it) or anything similar.

I do remember that it felt more natural. I think it would also feel less accurate, or at least strange, when your doorknob trembles when you grab it.

Touch vibration feels like an extra step in between to me, but I like to keep it on, because I'm not always sure my N900 registered a press under high cpu load. A confirming tremble is pretty nice sometimes

Maybe it's just psychological, without vibration it feels more direct, which adds to the user experience.