We have cruised with Oceania seven times so that speaks for itself how we regarded this cruise line.
After visiting the Van Gogh museum and generally walking around Amsterdam we commenced our 23 days on Marina from 24 September to Barcelona, disembarking on 16 October. We thoroughly enjoyed the nightly entertainment and, as usual the dining experience was excellent, including the times we had breakfast in our room.
Most ports of call were enjoyable with a couple offering nothing at all. Think they were just a stopping off point for Oceania's excursions.
The penthouse suite was actually just a concierge level stateroom with more room. Nothing special really and not worth the extra money.