Excellent replacement for chrome's session buddy
Update: It is limited to 100 tabs and the new update made recovery from the backup impossible after it deleted all the sessions it had stored

It's not a bad extension. But it has serious issues. For example, I found a very severe extension breaking bug, but the only way to report this is to open a discussion in some Google group. No, I don't join Google, just to report a bug in an extension.

Secondly, it's not open source! Why?
If it were on Github, I already would've written a bug review and could've tracked myself how the progress on it is. Since this extension is not open source I can't do anything and I have a bad user experience.

Thirdly, due to above reasons, sometimes the extension does not work at all, because of the huge bug I found and I don't even know if it will ever be fixed, because the author does not let me report it on Github, where this project's source should be freely available.