Picking a codename is the best part of a project. At work I'm currently part of projects codenamed "spicy sausage" and "magic banana". They have absolutely no connection to the work involved, but are much more interesting than, say, "data visualisation version 2".
Indeed. To me, "12.04" means nothing, it's the same as "11.04" and "10.04". Two numbers separated by a dot. "Precise Pangolin" means a lot more - it's something memorable, and still shows clearly that it's a later release than the previous ones. "Beefy miracle" is also memorable, although I don't think I remember a whole lot of their earlier codenames. I recall "Leonidas", since it's also a Lithuanian name, but not much other than that... I guess they are just not used very often, people still tend to say "Fedora XX" instead of using the codenames.
The Fedora codename leads to some themes for artwork which may affect the default wallpaper. Fortunately wallpapers from past releases remain available in the package repository if you don't care for the new one. Beefy Miracle so far just has some fairly generic fireworks wallpaper. If nothing else, you get to learn how to set a system default the dconf way.