Twitter reports that 90% of users use official Twitter apps on a monthly basis. Sysomos disputes this fact by analyzing over 25 million tweets posted on March 11, 2011. Their data reflects that official Twitter apps accounted for only 58% while non-official Twitter apps accounted for 42%. A breakdown of market share of non-official Twitter apps: Twitter Clients 16.4% Ubersocial  13.1% TweetDeck