I've been test driving a few of the Twitter apps that were recommended to me and I think I've picked my favorite.
I started out with Twitterific, which isn't that terrific. Nothing bad about it, but it just didn't stand out to me as the defacto app.
So, I loaded Twittelator, Twinkle, and TwitterFon. Twinkle was the early front runner because you could see people near you and what they were saying. The deal breaker was when I tried on multiple occaisions to send a picture with the app and was either kicked back to the "desktop" or given a server error. FAIL.
TwitterFon was good, but it doesn't have the added features like location and pictures. That leaves me with Twittelator which only has one issue. It only shows me so many tweets and won't load anymore. I'm sure this would be fixed by paying for the Pro version, and I might do that soon. Otherwise, everything works just as promised. Even pictures!