Well, the big issues, anyways. If we go for the small ones, I'd take all night.
1. Killing characters off off-screen. I realize the book is long, but my top five favorite characters managed to survive the whole series only for three of them to meet their demise off-screen in this book. That is pathetic. I understand that killing off second-tier characters increases anxiety, but why not at least give them a death scene? For the record, the two that survived were Kingsley and McGonagall. I'm sure you can figure out the other three.
2. Neville's role. He was supposed to come into his own here, and she certainly made a good run of it up to the end, but...geezus! Couldn't she have at least given him something original, instead of setting up a list of improbabilities ending with him emulating the Harry hat-pull move? And for god's sake, let him go Inigo Montoya on Bellatrix. He's been waiting for 7 books for this moment, and Mrs. Weasley gets in there. Granted, the Mrs. Weasley scene rocked, but Rowling could have had anyone kill Fred. Neville was supposed to take down Bellatrix, and he didn't. I don't care if he saved the day, he could have saved the day and gotten Bellatrix too.
3. And while on the subject of Fred, why was that left unresolved? We had foreshadowing of what the twins did when there was the threat of death, but after Fred dies, there's no closure with George. We just never see George again. What the fuck is up with that? Mrs. Weasley gets her grief, but nobody else really does.
4. Dumbledore. He supposedly chose the specific moment when to die to 'save Draco's soul' or some nonsense. That was a dumb reason to die if he wasn't going to follow this idea up with other plots. He managed to predict that far in advance about the De-luminator, why couldn't he set something up to actually make his death mean something for Draco? At the end, we see Draco's still Draco. He doesn't change. So what's the point, other than the old Samurai movie adage that the sensei needs to die so that the student can finally find his wings and reach his full potential? For a character that is arguably the second or third most important character in the series, she could have thought it through a little better.
5. The last chapter. What kind of a shipper's wankfest was that? Yes, everything ends up okay. Yes, Bill's daughter is shagging Lupin's daughter. Yes, Harry respected his elders and named his entire family after dead people. What the fuck was the point? Why not resolve everything in the present day and let us figure it out, instead of dropping the ball on resolution after Voldemort, and skipping to a place where it's okay for our characters to have babies? Was it seriously just to answer the fanfic writers questions about who ends up with who?