Twitter clients on Android are one of the areas that still need work, so we're always happy to see new competition. TweetCaster is promising to be faster and more fully-featured than anything else, and has dropped into the Android Market today.
All the usual functionality you'd expect is onboard, including photo support, URL shortening, profile views, threaded conversations, favorites and DM/replies. You can also have multiple Twitter accounts active simultaneously, something missing from a lot of clients we see.
There's a free version (with banner ads) and a Pro paid-version for $4.99 up for grabs. We've been testing out a pre-release beta version of TweetCaster for the past week or so; expect our review up later on today.