Did you have to go through a lot of trouble to get that day-one game? Tell us the story!
Yep. It was Mists of Pandaria. I went to one of the local stores around my house to try and buy the game and they didn't have any on the shelf. After asking about the game, they went into their stock room to see if they had any. Of course they didn't, so I went to another store. I asked about the product, since they didn't have any on the shelf. They said they would check in the stock room. Nope, no game. So I went to a third store. Same thing happened. No game. By this time, I was tired of searching for someone that had a copy and since I was busy doing the new pet battle-related stuff anyways, I decided to hold off for a week or so before going to get the game.
Long story short: Eventually I did get the game, and because I had to wait a little while to play the new Pandaria content, there weren't as many people out in the zones competing for quest objectives. I did learn something from this fiasco, though. Purchase the digital copies, then you don't have to worry about the stores having the game in stock.
Oddly enough, this also happened to me when I bought D3 and RoS. The only difference is the last store that I went to actually had the game. Only one copy left (which I got), but still. I guess the stores around here really need to order more copies of Blizzard's games.