Been playing some Senran Kagura Pinball and it's alright. It's chocked full of the fanservice that you'd expect from the series and it's liberally sprinkled throughout the story bits and the gameplay bits. As far as the gameplay goes, it's pinball. Aside from having some minigames on the board that unlock during various situations, it does what pinball does: you knock a ball around the table and try to rack up big points.
Only thing I have a bit of problem with is that you can "beat" the table and still have balls left [you play a certain minigame 3 times, and it's hard to avoid playing it], so you can still have balls left and the game just kicks you out. Not a huge deal, but if you goal is points [rather than advancing the story], it's a little frustrating.