Sure, the actors meet up and especially the guys got along fine. But that doesn't mean the set was a fun place. Garrett Wang in his Geekson audio interview says that the set often was tense because Mulgrew was unhappy with the direction the show had taken and she was taking it out on her fellow actors. Mulgrew herself admits that she was not happy (see above) and now Jeri Ryan in her Aisha Tyler interview has also said that she wasn't happy on set especially when she had scenes with Mulgrew.
Since Mulgrew was in a sense the leader of the company troupe as Stewart was in TNG and Bakula was on ENT, she basically set the tone. And that tone I've come to learn from these interviews was pretty grim. It's a shame, but as I have said above, to me these stories also say a lot about the producers and showrunners and their lack of passion for the show they were creating.