It is but folders on top as well as a few other features don't work or don't work properly.
It does have some glitches, but for the most part it works as advertised on my computer (a non-supported Mac Pro 1,1 running Mavericks). Some people seem to have a worse experience than others, some even reporting odd error messages, etc. Unfortunately, I can't provide any solutions for such shortcomings, as I haven't experienced them myself. In any case, it seems to me that beating the quality/price ratio of XtraFinder is hard to accomplish, considering the would-be competitors can't really guarantee a trouble-free ride for everyone in every possible scenario.