
I for one am pretty sure that LV went to Godric's Hollow with no other intention than killing Harry and using his death to create another Horcrux, as DD said. We do not know if he actually got around to perform the magic necessary to create a Horcrux, simply because we have no idea if you have to do it before or after the murder. To me, it seems as though JKR deliberately left that open, which makes me assume that there's going to be another twist concerning the creation of Horcruxes. But remember that the reflected killing curse took the whole house down, quite uncharacteristic of Avada Kedavra.
What bugs me is this: if LV went after Harry that night to make a Horcrux, he would have taken the object he meant to bind his soul to with him, right? What happened to it? Wormtail may have taken Voldemort's wand, so theoretically, he could have taken any other object, too, but then, he must have known about LV's intention for it, and I highly doubt LV would have shared that with someone like Wormtail. And DD would have investigated, of course...that doesn't quite make sense...
And you honestly believe DD is right about Nagini? I mean, in HBP, we see Harry go through all those memories to discover every little detail about Riddle's past that could be a clue, a lot of suspense is created because we're repeatedly told that Horcruxes are the key to destroying Voldemort but we just don't know what they are, then the big revelation, the guessing, and then DD says something like btw, Harry, Nagini, too. Just like that. What an anti-climax. Really, when did JKR ever tell us something right away? I bet the only function of that assumption is to tell us that, yes, a living being can be a Horcrux. Foreshadowing, anyone?
My problem is that Horcux!Harry is simply the perfect way to explain Harry's and LV's unusual connection. But yeah, the holes.
And you don't think Harry could be an accidental Horcrux? Even Voldemort himself might not have realized it, after all, he doesn't feel the pieces of his soul anymore. Consider this: He was after Harry all the time, until he tries to possess him at the end of OotP. Suddenly he changes his goal and goes after DD instead. Suddenly he realizes that his connection with Harry is danger to him, why exactly? He explicitly tells his Death Eaters to leave Harry alone.
Again, arghhh!