We've had late dining on all of our cruises. It works for us because we don't have to rush back onboard on port days, and we eat that late at home anyway. We may have a bit of trouble the first few days because we'll be eating earlier than we're used to due to the time change!
We've only skipped the main dining room once, other than for Palo. I had a horrible migraine, and leaving my cool, dark room just wasn't going to work. That's one really good thing about an inside room--they can be nice and dark when you need them to be!
As for tablemates--I'd say go for it. If you get awful ones, you can always ask to be changed to a different table. We've never had really bad tablemates. We've had some that weren't very talkative, but most of the time we've had great times! Twice we were seated by ourselves--once because we changed rotations to keep the same serving team on a b2b. The second time we were at a six-top by ourselves, but our servers also had a very large table which seemed to be a family reunion, and I imagine they had all wanted to sit together. The six-top was a big problem for us. Our servers kept bringing us enough food to fill the table "so that we wouldn't feel lonely"!

And, of course, there never seemed to be anything left at the end of the meal. No wonder I had to lose 20 pounds when we got home!
Beth