It's actually a fairly engrossing and deep game. It has little of the elements that drag down western F2P games (pay2win games anyone?) too, so that's a definite plus. Finally, it has a huge amount of content for a free to play game and is being updated at a constant rate. Recently, there was an Arpeggio of Blue Steel event from December 24th 2013 to January 6th 2014 that brought characters from that anime in and had various rewards (furniture for Admiral's office themed on the show) and you could even use ships from the show in other parts of the game while the event lasted.
In short, I personally think it's worth the trouble to get in.