Best bang-for-the-buck grouppo available, hands down. Rear derailleur shifts smooth and fast. Easy to tune and stays in tune for long time before requiring minor tweaks. Proved its durability in multiple crashes during cyclocross season. The overall performance of the Rival grouppo made me a convert from years with Ultegra and Dura Ace.
No bad features. It's not as lightweight as it's Force and Red siblings, but those handful of grams aren't very important. I'm 185, my 61cm 'cross bike is 18, for a combined weight of 203 lbs (92kg)....even a 100g difference at that point is less than a 0.005% difference in weight. Think about it.