Everyone's least favorite muggle family got a lot of coverage in JK Rowling's latest Pottermore update. If you're partial to reading it yourself, you can do a puzzle on Pottermore to unlock the new story or just read it here. If you just want the highlights, read on:
Uncle Vernon hates Harry because he looks so much like James. Once again, Harry's strong genes that leave him looking like his dad have come back to bite him. Vernon Dursley and James Potter didn't get along, so seeing Harry is just a constant reminder of a dude Vernon hates.
Petunia, on the other hand, feels guilty about how terribly she treated her witch sister and takes that out on Harry. Petunia was jealous of how much attention Lily got from their parents, and secretly wished she too could have been a witch. Petunia cut Lily out of her wedding, and upon hearing of Lily's death, was racked with enough guilt to take Harry in. Apparently that guilt wasn't strong enough to help her treat Harry decently
In another interesting tidbit revealed in this update, Rowling describes how Hagrid and Dumbledore got their names:
The colours red and white are mentioned many times in old texts on alchemy. One interpretations is that they, like base metal and gold, represent two different sides of human nature, which much be reconciled. This was the inspiration for the Christian names of Rubeus (red) Hagrid and Albus (white) Dumbledore. These two men, both hugely important to Harry, seem to me to represent two sides of the ideal father figure he seeks; the former is warm, practical and wild, the latter impressive, intellectual, and somewhat detached.
Aw man, why couldn't Hagrid and Dumbledore have raised Harry full time? Stinkin' Dursleys.