Never flown a 172RG, but I have flown Cessna RGs 177, 182 and 210. In my experience the hardest thing to master (?) is getting into the mindset of slowing the things down in good time - particularly with the heavier 210, it's amazing how much more slippery they are with their legs up. It's really easy to underestimate how much time/distance you need to get properly set up to join or land, and be left with the options of (a) dangle the Dunlops, slam the throttle closed and the prop all the way up - not wise, (b) some combination of the above plus aerial ballet - also not wise, or (c) b*gger off and come back with it sorted !