I like Neville, and always have. I thought McGonagall said his problem was a lack of concentration, not confidence, but either way, this was pretty close to my (and others') theory before OotP came out, but it had nothing to do with excusing/denying Neville's problems. The opposite, if anything. Basically, the idea was that Neville was seen as a very weak wizard and called himself "nearly a Squib." But that was nonsense. He frequently screwed things up, but he did so in dramatic fashion -- things exploded, table legs disappeared. IOW, lots and lots of power, absolutely no control. Which is, indeed, his own fault (though there were also psychological theories about said lack of control). Except, of course, that using someone else's wand really *could* lead to being unusually bad; I don't like that reason, but it is at least partly canon. (I wonder how many people start their Hogwarts career with a hand-me-down wand? We know of at least two.)

I also don't like the idea of Neville conforming to other people's standards of what's right or great. I could theorize that his dueling improvement is, as Harry noted, due to motivation from the Lestranges' escape, but he was improving noticeably before that. I have no theories beyond the fact that teenagers can change drastically.

I don't like the memory charm, but it seems like something that "helpful" wizards would do. Though I agree that if Neville was there, they'd have tortured him.