Starting with the positive: All the people who work on the ship are hardworking and helpful, they really aim to please. The ship itself is fine - middle of the road in terms of new/old. Things are in basically good shape. The excursions in Alaska ranged from the terrific to the mediocre, and the ship's activity desk (staffed by an overwhelmed ONE person) was not much help at all. So, it is up to you to do extra reading BEFORE YOU GET ON BOARD (or better still, before you book the trip) to see which of the options works best for you. Note that you can do the same excursions if you book them on your own. They will be cheaper and just as good (we did not realize this until it was too late, so we overpaid since we did everything through the ship's offered excursions). If you select well, you can experience some amazing things. Stay away from long boat rides or whale watching. Active choices are better, and those that include something unusual (float plane to remote area, helicopter to glacier) are better options.
Negative: The food is simply awful. At times, inedible. Every restaurant was just plain bad. The grill on the deck was edible, thank goodness, but not great. And get a load of the tortilla chips and salsa they serve before the meal: we were 8 at the table and there was a total of 22 chips (yes 22) on the platter for all of us to share. Breakfast buffet reminded me of a college cafeteria back in the 80's (newer college cafeterias beat out the ship's by far). Desserts were tasteless and awful. Heard of losing weight on a cruise? We all did. In addition, one member of our group got food poisoning (hamburger on the deck for lunch - avoid at all costs) and spent the night vomiting (ship doctor was rude and inept - after receiving a call that the patient might be having a heart attack, she showed up about 10 minutes later with a small doctor bag - no defibrillator, not even a blood pressure cuff - if this had been a heart attack, the man would have been dead. Good lesson to note: do not have a heart attack on this boat - you will surely not receive lifesaving care.)
The activities on board were pathetic. Shows were comedies (but were not meant to be funny). Ship director was a bit of a prig, even during his direction of daily trivia contest. Diamond advisor guy was as snooty and brusque as can be - his demeanor was totally off-putting and surely discouraged sales among my group.
All in all, I would stick with oceania. Steer clear of silver shadow. The staff really tries - the butlers, waiters, etc. But all the rest is mediocre to just plain bad.