Nero wasn't a bad character, imo.
Not to be picky or anything, Nero lacked originality. I think Capcom should have come up with something better for him. He's too similar to Dante. Appearance wise, and gameplay wise (disregarding Devil Bringer and the modes that Dante has). To us hardcore fans, we'll automatically assume he's just a Dante-wannabe. I didn't like his voice much. (Seriously, Ichigo?) Capcom got writers block and thought.. Young Dante... Blue template... Glowy arm... OMG PROFIT.
Nero was more of a... "HEY HERE'S OUR NEW CHARACTER, HE BARELY HAS A STORY BUT YEAH" type. Loved the Devil Bringer, and overall Nero as a character, I'd rate him a 6.5 out of 10. Mostly because as many mentioned here, he was half assed. And Kyrie wasn't too great either. She looked exactly like Orihime, another Bleach character, AND her voice actress happened to be the same.