I'm looking into buying new bindings this year and I've only heard good stuff about the delta's, but there isn't a lot of feedback that I could find. So I'm an intermediate rider and I ride park almost all the time (rails, boxes, small kickers, bigger jumpp...everything) and I own a Rome Graft if that helps. Also recommend other bindings (not too expensive).
If you are looking at the 09/10 Deltas I would definetly recommend buying them. This year ride discontinued the Beta, so the ride got a bunch of upgrades from the beta bindings like the ankle strap, base dampening, and gel toe strap. They also use the wedgie footbeds which are awesome. I'm waiting to get a pair of them as well
i have delta mvmnt dfc's and love them, definitely very responsive and sturdy yet flexible. I would recommend them to anyone who rides about 30% all mountain 70% park. As for the 390's some of my friends who spend almost all of their time in the park love them. I hear they are more flexiable then the deltas and have some cool features to them such as the straps have like a spring action to them so you can step cleanly into the binding without having to hold them out of the way. Either way i dont think you can go wrong, two great companies and two great sets of bindings.