i'm about as fast as i was on my treo, but that is with apple's dictionary/learning feature - i was this fast on my treo with full accuracy
overall i prefer actual keys and i find myself wanting to type shorter responses (if i'm responding to OT) or shorter emails/texts...was definitely faster on the treo
so far of everyone i know that has an iphone, the majority really like the keyboard (although they go through liking it and not liking it phases) but everyone who doesn't like the keyboard as much as their previous phone came from a smart phone with a full qwerty keyboard while everyone who loves it had a flip phone or something similar
it's not bad, it just isn't as enjoyable to type on as the treo...but the lack of a physical keyboard has plenty of advantages as well, and overall they far outweigh the disadvantages to the phone