I'm always always going to really like these types of shmups, so long as the soundtrack is cool, the visuals are nice and the shooting feels good. AD2 succeeds with all of that. Very fluid, lots going on but not too much most of the time (so it isn't totally overwhelming, not that that's necessarily bad). You can watch weapons on the fly and upgrade them... not especially deep but it's a beneficial little touch that just adds to a great experience.