We have been to Canaletto on Westerdam, Eurodam and Maasdam but not Oosterdam. They are all the same for the ships that have that restaurant.
We found the food good but not great. Our service was consistently good and it was a nice change of pace and enjoyable. The antipasto tray they pass is one of the best features IMO
We'll probably eat there once on our upcoming Maasdam cruise so clearly we like it well enough to keep returning.