Back here I wrote about my search for my 'perfect' Twitter client. Since then I've tried Seesmic and now MetroTwit which is my current favourite. Having not gotten on very well with Adobe AIR based clients (probably due to my own expectations rather than there being anything 'bad' about them as such), I've tended to look for clients written in the technologies that I like working with, WPF or Silverlight. Both Seesmic Desktop and MetroTwit tick those boxes.