Just implemented a tweet UI using MGTwitterEngine last night.  I had heard it was easy, but I didn’t think it would be that easy.  I think it took me about 10 minutes to figure out I had the wrong code revision and about 2 to actually implement the twitter bit.  It was so easy I ended up adding bit.ly support to the UI as well.  A note on that is that just because you get a response back in XML (or JSON), doesn’t mean you have to use libxml or NSXMLParser to parse the results.  A regex works just fine for finding a url between <shortUrl> and </shortUrl>. I recommend RegexKit Lite.