There are so many Twitter apps for WP7 that we tend to ignore new contenders…unless they really do something impressive and Birdsong seems to be pretty damn fancy on paper. Check out this feature list:
Configure your home screen timelines – add up to 5 timelines, in any order (including lists and search results).
High performance, infinite scrolling (no "load more" buttons).
Integrated picture viewing with all major picture sharing services (twitpic, yfrog, flickr, plixi and moby).
Threaded conversations for replies and direct messages.
Direct messages threaded and organized like an email inbox.
Intelligent local cache enabling offline viewing.
Map previews and Bing Maps integration for geo-tagged tweets.
Share photos with TwitPic integration.
Integrated web browser – no need to leave the application to follow links.
Status Bar – showing unread message counts for each timeline.
At-a-glance icons in your timeline let you see enhanced information for each tweet such as photos, location and conversations.
Explore your friends’ profiles, timelines and connections.
Fully integrated with your phone’s theme and accent color.
The offline caching without additional ‘load more’ is worth the price alone for me. Man I hate getting into a subway just to find out I have about 20 Tweets and the rest aren’t available. But check out their site for more images. This looks like the real deal. It’s $2 but there is a free trial.
And they’re already working on features for v1.1 (I’m guessing live tile support and toast notifications for messages).