So far I like TSM, it works for me without the problems others have been reporting. I am coming from the old Session-Manager and now I miss only a few but IMO important things at the moment.
First and for me most important would be the option to choose where to store your sessions. For example I go out to clients to show them some things on my laptop which I have I have previosly preselected in the office on my desktop. If I could save my sessions outside in the cloud I would have my presentation at a fingertip.
Also I would very much like to see a 'save window' feature, like there was in old Session Manager.
To use an anolgy, a session might be seen as a directory with the single windows as files. For effective filemanegement these extended features would IMO be needed.
As a minor perfomance thing I might mention that I miss the window oriented start of session-manager somewhat, it seems to be a lot slower to open each tab one after the other (at least on 7 windows with 250+ tabs that I've just imported as a test).
Anyway I look forward to the further development of this very much needed addon!