We are in our mid 60's and have sailed 7 times in last 7 years. After 2 cruises on Celebrity Millenium ships we decided to go upscale and try Oceania Marina in 2011. One month prior to sailing, we were offered and accepted a bargain upgrade from concierge to penthouse level. We were hooked and have booked penthouse ever since. First 3 cruises on Marina were excellent. Cruise on Riviera (Miami to Barcelona - April 2014) was great but food was down a notch (too salty) as was passenger respect for dress code.
Latest cruise on Marina (Tahiti to Sydney - Feb 2016) was equal in food quality to Riviera, i.e. slightly less quality than 2008 - 2014, or perhaps we are getting more fussy. Respect for dress code has clearly deteriorated. I suspect that the recent competitive pricing has attracted those who normally cruise on Celebrity, Princess, Holland America, NCL and as such the guest mix has changed. Many passengers do not understand "country club casual" as they are likely not members of a country club. Lack of young families on Oceania is still a good draw for us.
La Reserve and Privee as well as 4 specialty restaurants is a big plus. Excursions are over-priced and under- delivered but we realized that a few cruises ago, so we arrange our own. Lack of quality entertainment is a minus. String quartet was high quality, but pianist is still not up to par.
Experience was such that we are now considering alternatives, from Celebrity Aqua Class to perhaps a 6-star experience (Regent, Crystal, etc) or perhaps Azamara that competes head to head at 5.5 stars. So in our opinion, Oceania is certainly good but no longer great.
Penthouse cabin was great as usual. Deck 10 was chosen to reduce huge overhang on deck 11 and provide more sunshine. We chose port side by mistake, so we did not enjoy nightly sunsets from our veranda. Butler was great. We did not use executive lounge on deck 11, despite the short climb from deck 10. But in any event, coffee at Barista is a better start to the morning. Vanity & walk in closet are great. Cabin size and butler are great and worth the extra $150 or so per day.