For all of you who didn't play when Mirrodin was legal: just be happy you didn't have to put up with Clamp Affinity. It would be roughly akin to legalizing Deoxys-A in UU.
I regularly PTQ, have qualified for nationals, and have been to several GPs. Haven't Q'd for any Pro Tours yet, but I have attended two qualifiers this season and plan on attending seven more around the midwest in the hopes of getting a plane ticket to Hollywood. A bunch of my friends have been on the Tour for the past few years and they've traveled all over Europe and been to Japan like two or three times, which looks like an awesome experience.
As for anyone looking to learn how to play competitively, I highly recommend downloading MTGO (Magic Online) and start from there, as it is easier to visualize many of the more difficult concepts that new players have a hard time comprehending (the stack, mana pool, triggered and activated abilities, etc). I was pretty terrible at the game until I did this. It also gets players into good technical habits; it's amazing how people show up to events and not even know what the phases of a turn are.