You can get Beezz for FREE in the Marketplace. I also like clients that let you add text to Retweets, but Beezz doesn't let you do this yet. The main thing I see missing is conversation view. It looks similar to the original Twitter client, but does have a few less features.

Beezz: The client I have been using for that past few weeks is Beezz, primarily because of the Toast and Live tile notification support that makes it easy to jump back into the application.

There is no conversation view or notifications, but you can use it to have your Tweets read out loud. The application is available for 99 cents and there is no trial version to test out. I don't like that so much of the display is taken up by headers and the Metro UI though and would like to see more usable screen real estate. Twitt - A Twitter Client: I used the Twitt application back on my Windows Mobile 6.x devices and it appears to be a decent application.If they can get notification support soon then this will likely become my default Twitter client. I love the conversation view and the integrated web browser that lets you follow links and stay within the application. It has a very nice threaded conversation view, configurable timelines, integrated photo viewing, integrated location previews, and an integrated web browser. Birdsong is available for $1.99, but there is a free trial that lets you check it out a bit.

Birdsong: This newest Twitter client just launched yesterday.

Twitter client for windows 7