I've been running a production app on Edge Rails (straight from SVN trunk) for about a month now and it's been all good. The new-ish REST routing enhancements are great once you get your head around it. I also like the ideas behind the performance enhancements, though I haven't had a chance to really flex them yet.
Beware though, they "yanked" out a lot of common things from rails core, so if you are upgrading an existing app you may spend quite a bit of time getting things working again.
Looks like a nice, solid release. Lots of fixes, lots of tweaks to make things cleaner, easier, and more flexible. Nothing game changing, but a very solid job by the core team.
much as I not so much a fan of rails these days, I do like the way they have embraced HTTP in all its "glory" - its a simple solid protocol that is well known. Why not embrace it !
Beware though, they "yanked" out a lot of common things from rails core, so if you are upgrading an existing app you may spend quite a bit of time getting things working again.