I just bought Asset Forge (Deluxe!) today, and I love it. My only complaint is the file browser, used for opening and saving files.
You've made a pretty decent file browser, as non-native file browsers go, but why? On my Mac, I want my standard Mac file browser, with my standard favorites on the left, the ability to create folders while saving, etc. etc. On Windows, I'd expect the standard Windows browser there.
This isn't hard to do in Unity using the Native File Browser plug-in. I've used this in some of my own apps, and it works fine — the only trouble I ever had was taking care to catch any exceptions that might be thrown while opening a file, since if you let them percolate all the way up to the plugin code, it crashes (or used to — I think they may have fixed that). But a simple try/catch block takes care of that. And you get a 100% native file UI on each platform.
Please consider it, and if you want any help integrating it, just contact me. I'm a professional Unity developer and would be happy to help out, and no charge, because Asset Forge is so cool. :)