I thought I'd add my $.02 to this thread. I'm working on an iPhone app that uses the Twitter API.
This is a side project for me with a small budget and tight timelines. I'm using Matt Gemmel's Objective-C library to integrate with Twitter. Everything was going along smoothly, until I realized that in order to get Twitter to acknowledge my app (i.e. tweets from my app say "from web" rather than "from [my app]"), I need to use OAuth. (Older apps are being "grandfathered" in. How nice for them.) Matt's library doesn't support OAuth, and attempts by others to patch it have been less than successful. >From my perspective, the requirement to use OAuth has added days of overhead to my project (blowing my estimates) and negatively impacted the user experience. For what it's worth, I agree completely with Josh; OAuth isn't adding value to anyone in this scenario. But it seems I've arrived too late to this party. :-( - Michael
