The point of a "beta" hubski would be to allow users to switch back and forth. Obviously it isn't something you'd want to limit to the chosen few, it's something that would be an "alternative" presentation of the content that would allow people to play with the new toys to see what they get. If beta.hubski.com and hubski.com serve up the same content but one uses new rules and one uses old, it'll be pretty obvious to everyone what the differences are and whether they like them. You could even put a toggle in the header bar, the way demonoid does.

RE: Tags

Say what you will about them, they work for Getty Images. They work for Flickr. They work for Facebook. They're a fairly accepted shorthand for finding things that interest you - but, as with most things, they rely on a common lexicon. You might be interested in an article I wrote called "Reddit 2.0" which exists only on /r/ultrareddit. My idea was to overlay a new UI for Reddit over the old code such that people could play with Reddit 2.0 without disturbing the million-odd users in their hovels. Of course, it was mostly used by violentacrez to imply that I'm a nazi, but that's water under the bridge. Be it as it may, taxonomy is an important part of anyone's experience. You can't escape it. You can be resistant to it, but people will categorize a movie as sci fi or romantic comedy. People will categorize writing as essays or fiction. People will categorize photos as kittens or cityscapes. It's how we address the world. Denying that sort of taxonomy to users won't change their way of thinking, it will cause them to end-run around your functionality. Better to deal with it than let a "black market" develop.

Apropos of nothing, I'm drunk.