what happened to the original? Rated 2 out of 5 stars

Is there some reason why more screen real estate has to be wasted with toolbars on multiple windows when the original split browser extension worked great? Since the developer has decided this design is somehow "better", would someone please pick up the old extension and update it to stay current with Firefox changes? Heck, until the recent point release, I was able to keep it working through 10.0.0 by changing the rdf file in the xpi. Splitting is a great idea, this design is not.

This review is for a previous version of the add-on (2.0.2012012901.1-signed). 

I think you are unaware of broken behaviors of the old Fox Splitter (1.x) on Firefox 10.

Or, it is only by blind luck that the old one works for you with Firefox 10. I cannot maintain such a huge (and spagetthi) code anymore. Even if it become incompatible to Firefox 11 or future versions, I cannot fix the bug.