We've sailed Oceania before on their R-Class ships, but this is the first time on the Marina. We have been in Barcelona before, so we just came in the day of the cruise. The ship's connection via bus was a little clunky; we'll just hire a car if we return there in the future (cheaper, faster and more comfortable).
Boarding was smooth; Oceania registers folks in three classes (Penthouse & up, Concierge and all others), but the process was smooth (except for some language barriers with our person) for all, and everyone was boarding by about 1200-1230.
The ship is beautiful; its feel will be comfortable to previous Oceania cruisers (doesn't repeat, but does rhyme, and getting around is quickly learned). High-end English Country Manor feel, excellent artwork, very good touches throughout the ship that are low-key but elegant. The Concierge and Exec Lounges were more useful than we might have thought; great place to get a snack, a map or to get info without trudging down to reception. Service staff was top notch and responsive to our needs.
We did mostly private excursions, but when we did the ship tours, they were well-organized. The wait for tours in the show lounge, though, was hot, humid and less comfortable than we would want. Oceania may want to consider assigning a few other locales for groups to meet and wait, thus avoiding the stampede when a tour number is called.
Food is rightfully one of the reasons to sail Oceania. The four specialty restaurants were very good; our favorite was Red Ginger. The Terrace Cafe, especially with the addition of the grill, is a good option any night you didn't feel like waiting or dressing up. For breakfast, though, it got pretty hectic, and seems as though they should consider removing some of the tables to create a better flow. The wait staff also seemed to get overwhelmed at times (not being timely with requested items) due to the crush. The Waves Grill is one of the best locales at which to eat an excellent casual lunch; their array of foods and options would be hard to beat. The Baristas is also a hit, although a redesign of the library would allow us to take our coffee into a nice quiet area without the passing throngs meandering by. Of course, we would also have wanted 2-3 more nights in one of the specialty restaurants...
We also ate in La Reserve one night. The wines were quite good, although the food wasn't significantly different than elsewhere on the ship, so we're not sure if we would do it again. Not so much that it was not good, but the meals throughout the ship are excellent, so it is tough to move another notch up for the locale.
Entertainment was acceptable, better than on the R ships, but not that much better IMHO. The show lounge also has a "low roof" feel and fixed row seats, which makes it difficult to sit if you're late. We would advocate they move to a small table/bankette configuration to make it more like a Vegas lounge. Another issue is the fixed show times around 9:45. With about a dozen ports, we were out most days, and didn't want to rush dinner, so we did not attend many of the shows. Perhaps they might, especially on sea days, consider an early show time, or two shows, so people could either eat early and see a show or vice versa. The string quartet played each evening, and we usually sat in on their mini-concerts. The location wasn't the greatest (in the big hallway leading to the main dining room), but people were respectful of those listening as they trundled by.
Disembarkation was smooth, and the transit to the airport went without a hitch. Oceania also provided port shuttles at 3 stops, and we tendered into the small Biscay ports (tendering is more efficient than on the R ships, but the wait in the lounge, once again, made for a mad dash for the tender line more than once).