My main concern is that dragons are the new Oblivion Gates. I think many other people here share my sentiments. Bethesda always seems to think 'Oh, we made something that looks really cool, let's rub it into the players face over and over again so there is absolutely no chance he might not get enough of it!'. I'd rather have a few meaningful, cool and fun dragon fights than 100 boring fights. Personally I think that dragons will become pretty annoying in Skyrim unfortunately. The first time you entered an Oblivion Gate it was cool, but now I hate Oblivion Gates and don't even want to play the Ob main quest because of them. I guess that it will be the same with dragons after a while.
I too fear that dragons could become like Oblivion Gates too, but when asked about the subject before, I think Todd Howard said that they still hadn't determined how common dragons should be, so my hope is that this means they're being careful to make sure that they get the right frequency for dragons appearing to ensure that they don't become annoying, but we won't know if they can do that or not until the game is released.
We must keep in mind here that I don't think it was ever said dragons would be common, it's been said there's no actual limit to how many there are in the game, but that doesn't mean we'll see them regularly, it just means they we can't potentially kill all of them and have no more appear, whether they're rare or not depends mostly on how often they spawn, and we don't know how often that will be. Now, Todd mentioned having at one point been chased by three dragons at once, but he told the designer that should be removed, so we're probably not going to see situations like that often in the game.