There are a lot of well known (community) names in the beta already.
I also signed in a while ago, but I got the feeling that the beta XSI Vray forums are not visited often, at least it's bursts of posts and then some silence again, and feedback on questions can take some time.
Looking at people participating it's mostly people working in production, so time spend on Vray is probably equal to that.
I think Vray for XSI has certainly a bright future ahead, but (and I haven't checked the latest build(s) lately) a little bit more integrating would be nice. As I signed an NDA, I will not go into details on any of this. So don't ask
I still have my eye on Vray, and am trying to look into it when I have time, although for the last months this is something i don't really have.
But a call to beta testers would be a good thing, as this would be out of the door quite sooner than we think.