I’m writing this post directly from the wordpress iPhone app.
The interface is clean and the only minor issue is typing on the iPhone qwerty. This would make writing large posts painfully slow.
The aesthetics are pleasing and the app responds surprisingly quickly to commands. I have been poking around and writing this for about 15 minutes and there hasn’t been a crash or any freezing.
All in all I think the most useful thing about this app is the ability to store basic drafts while out and about. Then once home you could firm up the idea and post it live.