Some character merging i was kind of surprised by was the extent they merged Jeyne Poole's Winterfell story arc with Sansa her story arc.
Call me naive, but i wasn't expecting the wedding and the subsequent bedding to actually take place. Perhaps i didn't expect that, cause in the books Sansa remains a maid. I guess they did decide to go light on it, since Theon 'only' had to watch what happened to Sansa. This HBO adaptation makes you feel bad for Sansa, far more so then for the Sansa in the books.
To the point where it's almost painful to watch, I hope her present husband doesn't end up King in the end. The writers here like to pull nasty surprises almost as much as Martin, OTOH they did kill Joffre off fairly quickly so I guess even they have their limits
Having the book and show is very instructive in regard to how to write to a tv vs a book audience.