The one thing I have been struggling with the Windows Phone platform is the Twitter side of things. I use Twitter quite a bit and moving from using Tweetdeck on Android to Windows phone was difficult. The official Twitter app is nice, but it cannot remember your place in the timeline. Seesmic had the same problem along with several other Twitter clients. The one thing I did like using the Twitter app was getting live tile updates for mentions.
Rowi has a nice metro style to it. It displays your timeline, mentions, direct messages and also any searches appear in a seperate column. It also nicely remembers my position in the timeline, it will load the most recent tweets and if you want any missing tweets you just tap where it says “load more” and it fills in the gaps. I also like how you can set up a search column and it will refresh it like any other column. My only slight problem with the app is waiting for each column to refresh as there is no refresh all option. But in the main I prefer it to any other Twitter app. The app comes in a lite version or a paid version so if you like the look of this app you can give it a go. The paid version has live tile updates for mentions and messages.
Below are some screenshots of the app and here is a link to the Marketplace.