Used one in a 7620 for a while - it depends what you're trying to do. It'll kill flutter and won't hold you in tune if you break a string, but it WILL give you in-tune compound bends while leaving you with a semi-floating trem (it's not true floating, as it gives you a zero return point, but that's sorta the point).
I've been running a Tremol-No in my PWH and now CST for a while, and while it won't give you in-tune bending while allowing you to use the bar, it'll give you a truely floating trem that, at a second's notice, goes fully fixed and allows you to screw with alternate tunings and not go out if you break a string. They should be on the market in a couple months now, so that's the other alternative to keep in mind.
Haven't heard a hard figure, but I believe Kevan was shooting for $40-60 or so. Worth it - my prototype is built like a tank, and the final ones will actually have even stricter material tolerances (Kevan wasn't entirely happy with the surgical stainless alloy the shop that did the pre-production run used for the shaft - neither was the shop, for that matter, I think it ended up being a supplier issue).