Here are a few suggestions I would like to make for a next update:
1) The actual form added in the registration page is somewhat limited to select a "blog type". I would like to add here all the thematic categories used by Adwords as they have a comprehensive list and that they have translated in several languages... isn't that cool? (for the ones that might be interested you will find them here in English and in your Adwords admin panel for other languages). But such a list would require more than 2 levels of "blog types". And of course I want the users to be able to select several cat/subcats (maybe limited to a max. of 3).
2) I don't like the words "Blogs" and "Blog type" ("Blog type" is the name of the menu added in the admin panel). Could you change that with "Site type", "Site category" or something else? My users won't make blogs.
3) The plugin adds a new link named "Blog type" in the "Settings" menu. This menu is already rather loaded (can we say that? I mean very long), maybe you could simply add a new section in the "General" settings, just after the "Site language". That would make sense, wouldn't it?
P.S. I love this plugin. I think you have a lot of plugins that could be offering some cool features based on the "blog type" (Blogs directory (see this post), targeted advertising, ...)