Mostly they are visible at the top right corner and act as a minimap.
He will also add pistons (probably in 100 years...). A mod already out there.
Mojang should work on new stuff/more useful stuff or improve on already available features (powered rails, mulitplayer!!!!, new resources, more redstone thingies).
Yes, you could get a lot of these by mods, but they should've been in the game a long time ago.
Maps are probably a very low priority for the community.
I don't have a problem with the addition of maps. I only think that Notch doesn't give a crap about what the community wants most. Yes, you cannot please everyone, but why not please the majority?