Extremely useful but causes crashes Rated 4 out of 5 stars
I would give this plugin a 10 because it is exactly what I think a pane-splitting plugin should do (well, I really think it should come baked in..) and how it should operate, but it does seem to increase the likelihood of the browser crashing or freezing greatly. It might be due to incompatibilities with my other Add-ons (which I can't do without - Firebug and LORI).
Another very odd thing I have noticed is that firefox locking up and Microsoft Outlook (my work email client) locking up seem to be inexplicably related. Not sure what to make of that.
I would love to keep this Add-on installed but for now it's just not quite ready.