^^^ In terms of actual astronomy, the basis of the Mayan calendar, and what is happening in the sky, on that date is absolutely fascinating. If anyone can find a good website that details the level of sophistication of Mayan astronomy and mathematical prediction of celestial cycles, WITHOUT going into the seemingly unending 12/21/2012 new age mythos, it is a great story -- and will be an interesting pre-dawn morning for sky-watching if you live in the right part of the planet. There are a couple things that will happen that morning that won't happen again in any of our lifetimes, having to do with the relative appearance of the sun seeming to rise in the 'middle' of a large dark area in the milky way. This happens every few thousand years.
It might not be as dramatic as the something like the Hale-Bopp comet or anything, but if you like sky-watching, it will be cool and it is a 'unique' experience relative to the human lifespan.
And it should be noted that there are no extant Mayan texts that in any way indicate that the world will end at the end of the long count calendar cycle.