Alright, finished the demo twice.
Well, Bayonetta does make some very marked improvements to the Action genre. In addition to the Climaxes sweetening your victory, combos are fluid (provided you can remember them, because they're not intuitive, but that's on par for the genre), the controls are solid, and there is the one-button, catch-all Evade.
That said, it still needs work. DMC4 Nero's O-button arm was the last and only time I actually felt like I could tackle a boss. You do get a great sense of power fighting regular enemies, and she does make quick work of them. But when it comes to bosses or rivals, you are still at the mercy of your measly weapons. Any combos you pull may or may not interrupt the boss, leaving you no time to evade. That Evade function, by the way, is handy in that it's one-button, but you can barely see what move your enemy is about to pull whereas in other action games you have just enough indicator. Or you can at least see the bloody weapon or their arm swinging, for pete's sake.
[spoiler]I tried to think of it all as a backwards world where their Dark is our Light, etc., but that wasn't working out. I'm not sure I could play this game not on any part of the controls, but almost on a moral basis. Decent game, still.[/spoiler]