By now you can hardly have avoided the announcement. J.K. Rowling thinks, in hindsight, that Ron and Hermione were wrong for each other and that perhaps Harry and Hermione would have been a better match.
I was even more disappointed by Eric Crampton's take, a polemic replete with HPMOR quotes and a determination to ignore the fact that we're talking about an 11-year-old. Yes, Ron inherited some silly ideas from his parents (and from the Wizarding World as a whole) but he also had a cool head under fire and an admirable willingness to put his interests aside to serve others. In the first book alone note that, apart from his heroic sacrifice in the chess game, it was he who had the sense to think of lighting a fire when confronted with Devil's Snare.
I'm not going to attempt to defend the Ron/Hermione relationship - if they managed to be friends for six years and Ron only developed an interest in Hermione when she suddenly morphed into the actress playing her then I'm happy to lump it in with most late-teenage you're-fit-let's-date relationships, albeit with considerably more intense shared experiences than most. Harry and Ginny at least had complementary personalities - Ron and Hermione would never have become friends without Harry's influence. (If we're brutally honest, it's doubtful that Hermione would have had friends at all for at least her first four years at Hogwarts were it not for the troll incident - at least, not among the Gryffindors. Maybe she'd have bonded with Neville over neither of them having anyone else to hang out with?).
I remember one fanfic I read suggested that, in an alternate universe with no Ginny Harry would (being rich, famous, presumably good-looking) have had his choice of girls, and gone for the one who he found most interesting - Luna. I like this theory, and Luna would certainly be my favourite alternative to Ginny. I don't know that I'd say that Luna was the best girl for Harry, but I would definitely say that (of the characters appearing in the books) Harry would have been the best guy for Luna. He never mocks her, which puts him ahead of just about everyone else to begin with. Let's hope that Rolf Scamander was suitably eccentric.