They have pretty much abandoned the limits because during the initial rollout they found that they could let users do pretty much whatever they wanted to and still not incur crippling network overhead costs. If you look around the site you will probably find this info.
Go ahead and sign up. That part is free.
I just saw a blog post today from May 30th saying that they will be starting Beta Wave B in July and hope to have all the Waves rolled out by September.
They NEVER meet any of their scheduled dates. That part you can rely on.
The phones are unsubsidized and the three price points they are considering (tentatively) are $200 for the Optimus R, just like ours but WiFi hand-off enabled, maybe WiMax/4G, $300 for something 1 GHz with a 3.7" screen, hardly worth the difference in price over the Opt. R, IMO, and a dual core 1.2GHz unit that sounds a LOT like the EVO. But it's $500!!!
I get $100 off because I signed up back in November. :-!
You have to use one of their phones, so don't expect to BYOD. They will e-mail you a week before your Wave so you have time to get money together. I have already started saving because I couldn't scrape even $200 together in a week.