Rated 4 out of 5 stars

May just be with Firefox 20? Dunno. But annoyingly the "disable with key" preference when using "SHIFT" to disable doesn't work - on LinkedIn at least...

This review is for a previous version of the add-on (2.4.1-signed). 

TZP 2.4 working for me in ff 20 (on Mac OS X 10.8.3). Which operating system are you using? Please follow-up to firefox.add.on@davidadler.name.

Note that you must start holding Shift before you hover over the thumbnail, not after. If the pop-up is already displayed, you can press Esc to dismiss it.