So far Lego Friends are the clear winner in our house. Both girls have been putting together Legos since Christmas day and still have a couple more boxes to go. The iPad minis with iTunes cards (from grandparents) would be runner up. Up to this point we have only allowed free apps on their iPods...needless to say Minecraft was the first app to go into the iCloud, with Cut the Rope close behind. I added Stack the States and Duolingo (which is free). Now they are really giving some thought to what else they want to purchase and debating what they can get with the amount they have left.
The other set of grandparents got the girls gift cards to Build A Bear. This was a huge hit while they were in the store picking stuff out, naming them, and dressing them up. They played with them for a while but now they are just sitting there with the other gazillion stuffed animals they have. We are having a stuffed animal purging very soon!
Like Blackcat...they were excited about the Snap Circuits when they opened that present, but it hasn't been touched since then. I think it will be a hit, but I may have to drag them from the Legos to get them to open the box.
DD8 got the first "Olivia Kidney" book and DD9 got "The Phantom Tollbooth". Both girls didn't seemed very thrilled with those when they opened them, so I'd say for now that is a miss. However, I know once they start reading them that will probably change.