Speech2Tweet is a powerfull tool, not only thanks to the included speech to text conversion but also because it includes all the features expected from a full featured twitter client.

Among other features the security features have to be mentioned, since they are compliant to the newest standard provided by twitter and are a task for themselves (which can easiliy be seen when looking at the growing number of twitter clients that fail due to their lack of security).
A clear and easy to read interface goes without saying, other features are switchable automatic geotagging of Tweets on full screen maps and (switchable) automatic geotagging of pictures and photos or the possibility to enable the automatic update on the iPad or when connected via a WiFi network thanks to iser streams API.
URL shortening is as well a given as the inline web browser.
Twitpic image service is supported, ads can be disabled and reply, retweet and Direct Messages are supported as well.
Search for nearby tweets and user is another usefull ability of Speech2Tweet, many other features are included as well.