Rated 5 out of 5 stars
I installed this because of the option to use Bing Translator, which pops up with a translation right by the text, as opposed to Google and others that open a whole new tab to view a translation. This is much more convenient if you only need to translate a word here and there. The highlighting and other stuff is an added bonus, and it's been working fine (I had no trouble using the backspace key with selected text).
One minor suggestion: sometimes the popup menu gets in the way of the text that I just selected which is a little annoying; it you could somehow configure it to appear completely above the text that would make it even better. But otherwise I'm completely happy with it.
Thank you for the good review!
Popup position actually controlled by FF. Can you please report the issue on the support site and provide more details, maybe even screenshot, I'll try to correct the issue.
Update: in addition, v7 has 'popup button' option instead of popup, it may satisfy you as a workaround.