I have to begrudgingly admit I enjoyed the demo at E3. I also got some 40 minutes with it, including both a tutorial level and pain in the ass of a boss who randomly refilled her life (though I have the uneasy feeling it's because I failed a QTE). The fighting is fun, Dante sounds like Dante, even if he still looks like the emo kid we'd all met in high school.
I still don't know what's up with the story but you know what, I'd buy this. Not sure about 'day one,' but I'd definitely buy it. I play this stuff more for gameplay, anyway.