I managed to get into the beta, and was so excited about the prospect. I think one of the most serious problems at the time was scaling... A conversation with more than about 5 participants was just plain unusable due to how slow it was to update and display.
It has been five years, however, and computers have gotten much faster. I tried the test server, and while it has some display issues (flashing boxes during updates, etc.), it is very fast, and quite comfortable to use.
I think the only problem at this point is a social one... I can really only imagine two scenarios where this takes off. 1) The non-federation case gets incredibly compelling (e.g. if for internal company collaborated editing) and eventually there's so much use, people start setting up federation. 2) Niche (meaning targeted, not meaning inconsequential) federated use becomes common (e.g. if open source communities were to switch to this en masse in place of listserv), and people get so accustomed to using it that outside organizations start picking it up.
I'd love to see that happen, but at this point, I'm not holding my breath.
Sorry about the downloads page, you saw the page as prepared for an actual release - I have rolled it back to showing the last release candidate presented on the mailing list.
Feel free to ask me any other questions...