I love B2B cruises! The whole getting on the ship process (packing, testing, traveling, embarking) is a hassle and I only have to do it once.
Turn around day can be a pain but much less so than getting ON the ship.
In January we did a B2B on Oasis, western then eastern with CocoCay on both.
Week 1 we invested in the shore activities (bar hop in Cozumel, Maya Chan in Costa Maya, monkeys and sloths in Roatan) On the ship we just visited included dining. Week 2 we had the UDP and did very low cost shore activities. Plus we got to see Aqua 80 multiple times.
I enjoyed the trip so much I booked myself on a B4B for Oasis in February
Another thing about b2b, especially on smaller ships is getting to know the crew.