I've been playing since October the 8th, 2013. I'll try to answer your questions.
Attached image is the amount of XP required for each level up on a ship. You know, to give you an idea of the grind.
When you're new to the game, it's not bad at all. You have a pretty good time looking for girls you like and enjoying the soundtrack. Once you start to get a handle on the mechanics, things start to feel less fun.
After a while, you'll eventually reach a point where you've cleared most of the "story" maps and found the majority of the girls you want. At this point, the game becomes pretty damn dull. You stay logged in to the game running expeditions for resources/consumables and grinding XP in preparation for the next event. The events are why you put up with months of boring shit, though. They're hype as hell.
The game has a fucking fantastic soundtrack, good voice acting, and generally good art. Some of the girls have legitimately fun personalities. The game gets updates about every forty days that add things like new ship remodels or maps.
Most importantly, don't play it if you're expecting a lot of gameplay. The mechanics are surprisingly deep, but there's no actual gameplay. You just click buttons and hope that you've tipped RNG in your favor enough to pull a victory out of your ass.
Oh, and it has an in-game cash shop. Make of that what you will. I'll post some music when I can find a way to do so.