We did lots of
DCL tours and enjoyed most. Some highlights...
We absolutely LOVED the cultural tour of Berlin (the best), and the castles in Denmark (sorry, can't remember the exact names, so hope this makes some sense)!!
Thrilled to hear about the Cultural Tour in Berlin !! We just switched to this tour today !! 
The Hermitage (amazing) & Catherines palace was a good one as well - lunch included a shot of Russian vodka if you chose. :]
Helsinki with Porvoo & lunch was fun & a beautiful view of a quaint town.
In Oslo, the viking & maritime museums were small and way too crowded to enjoy, but maybe they will work out the kinks & not send everyone at the same time!
In Stockholm, the ice bar was too fun, but the walking tour was a bit tedious & the weather was turning cold (most stops had wonderful weather - so lucky, even in Oslo, we missed the rain w/ a shorter tour).
Our server, head server & room host all told us that 1600 was the final count, with 1200 return cruisers!!!!!