The very first thing I see is something I've never seen before, namely that Xtrafinder (Edit: 0.1) is a flat package...opened, and presumably meant to be installed, by Pacifist.
That may just be Pacifist 3.x monopolizing the LaunchServices database (inadvertently). I think Apple's Installer.app is what the package's author presumed we would use... presumably.
I was able to change the default "Open with..." to Installer with no problems, and I e-mailed the developer, but do you think I need to contact Charles Srstka? (I've never run into this behavior with any other app.)
For a 0.1 release from what looks like a brand spanking new developer, XtraFinder looks great so far, except for the fact that the "Folders on top" functionality doesn't hold for more than about 10 secs, at which time it reverts and I've got to navigate away from my original location and back to get another 10 secs.
Functionality includes "Show invisibles" (Doesn't require Finder restart.), "Restart Finder," "Copy path," and an uninstaller right in the menulet's drop-down, with more promised. (I can't imagine it remaining free.)