I love this little app. It's not the shiniest twitter app out there but it's free - and supports lists, which seems to be something many other minimal twitter apps can't handle.
My favorite thing about the app is having tabs for each of my lists. I use lists a lot- it's useful for "following" app updates, devs, etc. that I don't necessarily want in my timeline.
My only wish for this app is that it could live in the menubar with no dock icon. Well, and that it was a tiny bit more polished looking. But other than that it's great.