Using Witter 0.1.1-1 And I really like it! I'm a heavy twitter user and I really appreciate the effort.
I have some stuff for you to consider. They are in priority order:

Bugs (Haven't tried the devel version, so could already be fixed)

• Url actions don't seem to work on my device. Nothing happens.
• The long-click menu should also open where you click, because it disappears when you try to move to it otherwise, that's a bug I guess.
• Twitpic button closes the program, and nothing happens

Smaller suggestions

• In the long-click menu on tweets it would be nice to have a User actions -> view user. This could open in browser if you don't want to implement a profile viewer
• I'd like the timeline, mentions and direct messages to refresh the first time you open them since you don't open them to look at the empty screen. After that the manual refresh is a quite good idea.
• The long-click menu could have a direct message user option
• Search window should have the "Tweet" button removed
• I believe there are some nice shaded standard buttons that could replace the flat ones for a quick aesthetic upgrade. (Hildon.Button perhaps)

Stuff for the future

• Now that you have notifications and other fancy stuff, I'd like to see an option for some automatic updates with notifications. Separate option for autoupdate and notifications for the different areas would be mint. Personally I'd only autoupdate "mentions", and would use proper notification on that.
• Saved searches - This is something I use a lot on desktop clients to follow certain hashtags, for example one search I have is "#maemo" OR "#n900". Would be nice to have a set of them in the search dialogue that you could just click on to see.
• I'd like to see the buttons moved to the side because I find it easier to read tweets that are wrapped, and it's easier to scroll when you have a taller area to poke at.
• click hashtag in a tweet could go to search and search for that hashtag (Or search hashtag option in the long-click menu)

That's all I have for now.

I find witter very nice and usable even if you don't add any of the stuff I suggested. Keep up the good work