I hard a hard time finding it. I kept searching for Finder enhancements and dual-pane, etc. and I kept finding commercial/shareware ones that cost over $40 in some cases. I don't mind paying for a good program, but $40 is out of line just to get dual-panes, which is all I really wanted at the time. I didn't think I'd care for tabs in Finder, but it's really pretty darn nice, after all. I didn't even see a donation-ware request on this guy's site. I'd gladly kick in $10 for this thing just to encourage maintenance updates to ensure it keeps working with newer OSX updates. I don't know why Apple has never offered tabs or dual-pane with Finder to begin with. All these OSX updates and Finder pretty much still sucks....
The only option I had a problem with in XtraFinder is the color icons option. They look great (I hate the black&white sterile thing Apple switched to with iTunes awhile back and I'm glad to see at least iTunes 11 with its other quibbles at least brought color back). But Mountain Lion is still grey in many areas. The problem here is that Finder slows to a crawl with it turned on (it'll lag and then give a spinning beach ball for several seconds when I do anything; I turn color icons off and it runs full speed with no issues even with loads of other options turned on in XtraFinder).