This looks great! I am considering switching to this on NameTycoon.com...
The only sugguestion I would make, is to have the option to use a ModRewrite file to replace the dynamic URLs with false static ones, so a link to a domain would become:
And a link to a category would become:
This way search engines can index the whole site and not just the front page.
Other than that, it looks as good as any commercial product I've seen on the market.
Great stuff, Jon!