Just recently off the Regal Princess (Jun 4) 14D from Athens to Rome. I will share what we experienced as best I can, hopefully this will help. And Ill try to answer some notes of questions above.
COVID Testing: So the only testing we did was in Athens. That was a mess, by the way warning here, if testing is still required in Greece, they have changed the rules, so don't follow Princess's site. The rule now is you must present a negative witness PCR test within 24 hrs. The site stated 24 - 72 hours prior. That was not the case, as we tested using the EMed Kit (supper simple BTW) at the 30 hr before departure, and had to retest at the pier at no charge, just mad we had to retest for a 6 hr time difference. After that there was no mention of testing unless you report to Medical for an on-board illness. Some reported not feeling well, the tested positive and ended up on Deck 9 (Quarantine Deck) for 5 days to 10 days pending symptoms.
SHIP: The ship is a very clean and a well maintained ship. It was recently in dry dock, so its in great shape. Unfortunately, the crew is haggard and tired. Seems they are short staffed and parts of the crew is a little slow to move or are not interested in quality customer service at times. Room Steward William (Baja Deck 11) was fantastic. That said, you will find a few bright spots in the casino and the Main Dining Room. MDR was empty most nights, which was a shame, those servers are happy to see you, so plan to go and often. Many were standing around and helping other areas due to their area had no one. Food was good on some nights, and average on other. The breakfast buffet was terrible BTW. Same menu every day, no changes. Only changes was because they ran out of something. Frozen pastries thawed the night before, nothing really fresh but the fruit.
THE APP: Medallion Class thing has its quirks, but does a fair job. NOW, as for the Medallion APP and Wifi.... holy mother of all that is holy... Princess needs to either fix the App or abandon the project. That app was terrible and rarely worked, it's frustrating. In fact, the crew even joke as to how terrible the app is. When it did work, the bars will be a nightmare, so plan ahead. Often times when people ordered drinks through the app, the bartenders would focus more on those then the patrons at the bar. Ordering through the in room TV worked very well, and room service was spot on every time and fast. As for Wifi, if you plan to texted each other in airplane mode, or FaceTime family, the Wifi was spotty and unreliable. The best service was in ports, so plan phone calls and/or FaceTime to family on port days, sea days its a hot mess! Truthfully, as the wifi goes so does that horrible app. Use the Patters.
TV Filming: Someone earlier as about the filming of the show "The Real Love Boat", they were really quiet actually. Club 6 on Deck 6 is the only venue closed full time, and periodically an area will be closed for filming for a short period of time. A couple times you would see the contestants on the pool deck soaking in the sun, but for the most part they don't interfere with anything.
SHORE EXCURSIONS: We did all our excursions through Princess, and for the most part they are great. Warning here though, many of the longer excursions returned back the the ship late, and in some cases 60-90 min late. Of course they held the ship, but Princess needs to review the use of some of the vendors and start holding them accountable for tardiness. One vendor even laughed at the notion that we would return in time. So that said, take this solid advise please, pack some pre-packaged granola bars or snacks, you will thank me for that, I promise.
*** I will caution people on doing one excursion which is the San Michele Wine Tasting/Mt Etna Tour in Messina, IT. The winery treated the tour so poorly and could careless if we were there. They assigned the most junior worker there, stuck us in a small hot room, and you barely got a sip from three different wines. Never explained what we were tasting, then were offended that you didn't buy bottles of wine. The Etna piece and the guide was great, but the winery needs to be put on notice. Recommend a different tour. ***
Id be happy to share more if you are interested. Happy holidays, vacation, break from work and enjoy. Remember why you booked this itinerary, its a good one.