Having done a TA on the Marina in March 2012 we decided to try the inaugural crossing of the Riviera in Nov 2012. I guess we liked it because we've already booked for a 10-day cruise on the Riviera in March and another TA in Nov 2013. The Riviera and the Marina are almost identical - a few improvements on the Riv. Some of the crew from the M have transferred over to the Riv to add experience to the mix.
We enjoyed every one of the 14 days. The ship was not full and getting specialty restaurant reservations, deck chairs and space in the pool was never a problem. We liked Polo Grill the best and Jacques the least, but all of the dining venues are excellent. We actually enjoyed the Grand Dining Room the most. There were 3 lecturers, all of whom were very informative and entertaining. I'm a musician and I most enjoyed the string quartet from Poland. Their repertoire was amazing and the quality excellent. The evening entertainment was generally good. I attended two of the song and dance big production performances wearing musician's earplugs (decibel reduction with no distortion). After that I skipped them. That's just a matter of taste I think, not a serious complaint. My wife found a group of knitters who got together in the commodious Horizon Lounge each morning. The food is great, the staterooms are comfortable, the crew is friendly and accommodating. Most of the passengers were repeat Oceania cruisers, so what's that tell you. Having heard from those who've cruised on other lines I think I'll stick with Oceania.