Based on the scuttlebutt, here's my guess on the lack of a beta client. First, the client has been done for a year. It's the easy part, and even so it really doesn't matter if it's Intel native or not since all it does is start and stop the cores and handle uploads and downloads.
The hard part is the cores. The cores handle the actual calculations and you can't have beta cores out there potentially sending back incorrect data. That would really screw up the project. So cores will go from nothing to full release.