Rated 4 out of 5 stars

Would give this addon 5 stars except the button to open the SiteDelta sidebar is missing in version 0.13.1.

Don't know if this is intentional or not so I've reverted back to version 0.12.1 which still has this button.

If anyone wishes to revert to version 0.12.1 you will need to update the "install.rdf" file to show "em:maxVersion="13.*" />".
(NOTE: "13" refers to the Firefox version. Change this number to the version of Firefox you are actually using.)

It's easy enough to do, just change the extension from xpi to zip, extract the "install.rdf" file, open it in notepad, make the max version change, save the file, move it back into the zip file, change the extension from zip to xpi, then install the addon.

I will upgrade the rating to 5 stars if the author ever puts the SiteDelta sidebar button back.

This review is for a previous version of the add-on (0.13.1). 

The latest beta version from http://sitedelta.schierla.de/beta.en.php adds a "toggle sidebar" toolbar button again (however slightly different). I'd be glad to hear if you see this new button as a reasonable solution.