It doesn't look like they've added too much. When I use reason I usually master outside of the program anyway, and that new combinator (or whatever it's called) seems like it's not really doing much except making it easier to group your sounds together. I can get the same effect if I copy what I played in the arrange window to the different modules and tweaked it in there.
Even with the negative response, I'd still like to check it out and see how it all works and sounds. I'm interested to hear the new sound bank too.