My last ten cruises (and 11 of last 14) have been groups arranged by my TA. We have had as few as a dozen and as many as 115 (on a 700 person ship). My next cruise Montreal to Ft Lauderdale has a group of over 100 on a ship that holds just 490.
Groups are FANTASTIC!
We do arrange some dinners in advance (we all keep a dance card) but it is great to meet for cocktails each evening and decide with whom to eat and decide on a restaurant. The 115 was for a one week cruise so there were not enough meals to eat with everyone but we did try.
On our most recent 25 night cruise there were just 33 of us (out of around 425 onboard). We were able to arrange multiple meals with everyone.
We have our favorite card game and get together for cards or scrabble whenever we can. We will organize our own whisky tastings and teams for trivia and other games. I heartily recommend sailing with a group.
We almost went on one CruiseMates cruise but had to cancel when I was transferred to Tokyo. I would love to try again to go on a CM cruise; if not Regent (there was one CM cruise already on Regent) then on Azamara or Oceania.