tivopony, the TiVo employee that frequents the community boards, posts some details of the beta and hints at features that will be tested.
I'll tell you up front that it's a minor release, not a major one. But there's a lot of groundwork buried within. But should you get it? Well, if you own a 540 or a 590 prefix recorder that's experienced macroblocking with the previous release, you'll probably want this. If you have a TiVo-powered DVD Recorder or DVD Player and would really like to have TiVoToGo asap, you'll probably want this. If you'd like to have network support within Guided Setup, you'll probably want this.
Sounds like some bug fixes for certain models, TiVoToGo for the DVD recording TiVos finally, and another long-term request that goes all the way back to one of my first posts here over two years ago: allowing guided setup to use the network connection instead of a phone. [thanks Megazone]