I have that setup right now. I like it, but haven't run a lot on it or loaded it heavy yet - just set it up in November.
The bags are good quality and the NW rack works well with them. You have to adjust them a little to get them to fit as you like them but once that is done it is easy on, easy off. I have been in the rain with them and they are definitely waterproof. They are not super convenient to get into and out of during a ride because of the roll top, though. I got them as a waterproof bag that I can lift off quickly with decent capacity. They do that just right.