I really like the keys on my A-800, in fact when trying out various keyboards in the store it was the feel of the Roland's keys that sold me over anything else. I'm not a keyboard player but these seem to have just the right balance of weight and springiness.
The only weakness to this keyboard is IMO the touchpads. They just don't seem to be accurate or consistent enough to tap out drums on, especially when it comes to velocity. I don't know whether it's because they need "breaking in" or whatnot - to be honest I haven't used them much since I prefer to tap out drum parts on the regular keys.
The combination pitch bend/mod wheel joystick seems to work very well, although this is a matter of taste and I've heard some people say they didn't like it.