I have used TweetStats excellent statistics since the site launched. However, I find it less and less reliable and it can simply not work for weeks at a time.
I have found replacement apps and services for all the data points that TweetStats tracks except for two (that I find highly interesting): the clients I use the most and reply statistics (who you reply to the most and who mentions you most frequently).
The client statistic is important to me because I like seeing how my usage changes from device-to-device and from app-to-app.
Is there another service out there that can track this information? I feel like I have already checked all the possible Twitter analytics/statistics services—most of them do the exact same thing—there is.