I’ve been watching for it off and on all day, having seen an article about it late yesterday (and Ars Technica now has a “first look” article, as well). When I checked a few minutes ago, I saw that it had been released to the download servers late today. I running it right now on one of my Linux boxes and have seen no problems so far. Seems a bit faster than 3b2 and the UI has gotten a bit of attention, even on the Linux platform which saw a major overhaul with b2.
[Edit 8:35pm] OK, I spoke too soon. There’s a bit of wierdness with some of the dynamic stuff like address completion in Gmail. It will be interesting to see how soon that gets ironed out.