Some noteable features:
- A unique user interface.
- Works on VGA, QVGA and SmartPhone devices.
- Support for multiple twitter and identi.ca accounts.
- "Conversation View" shows a what this status was in reply to.
- Uses standard notifications to alert you of new frields statuses or replies.
- URL shortening with is.gd.
- Take photos and send to TwitPic.
- Integrated search.twitter.com.
- Clickable @names, URLs, and #Hashtags .
- Option to check for new version on startup.
- Themes.

Requirements:
- Windows Mobile 6 (it may work on 5, I'm not sure).
- .NET Compact Framework 2.0 or better.
- A network connection.
- A twitter or identi.ca account.

Update Description:
v0.52:
- Detailed view. Easier Ping.fm account setup.

v0.51:
- More bugfixes and optimizations.

v0.50:
- Fixes.

v0.49:
- Faster, Prettier.

v0.48:
- Fix a few bugs.

v0.47:
- Bugfix for reply ids.

v0.46:
- Conversation view, Hashtags, Themes, and more!

v0.45:
- Skweezer option, Quote function.

v0.44:
- Shorttext.com integration, better caching, smartphone account management fix.

v0.43:
- Copy+Paste in status update. More crash fixes.

v0.42:
- Less invasive error reporting. Don't get timelines from Ping.FM.

v0.41:
- Ping.FM fix. Selection fix.

v0.40:
- Avatar updates. No longer jumps to top on new tweets.

v0.39:
- Direct messages and replies shown under "Messages" menu item.

v0.38:
- Fix rendering issue for some clickables.