Great add-on!! I tried many before I settled on this. It has an intuitive UI, loads of features, and is really simple to use.

Some more features I would like are:
1) It would be more useful to save the tab-wise page history so that on restoring a session, I can move back and forth in history (granted, this may not work properly all the time due to caching, etc., but I still think access to a simple history would be very helpful).
2) It would be awesome if it were also supported on Firefox for Android.