ABSOLUTELY yes! I've been doing GTD for over three years now. I will be 26 in a month. My very first boss out of college introduced me to GTD--he got a copy for everyone in the office. The way I see it, those of us who start working GTD young have years to work with this and hone our personal practices. I think of it like putting into my retirement fund (you do that too, right?)--the longer time I have to work with this, the greater the benefit that can be gained as I really trust my system and am able to spend time making decisions at the higher altitudes.
And seriously, we're at a fantastic time to start implementing GTD--it's precisely because young people don't have as much to track that it's so much easier for us to get in the habit. Even though I have a fairly complex job, my home life mostly consists of keeping a 13-pound cat happy. So, when I weekly review, I can sweep *everything* out of my mind and into my system without having this huge unwieldy system. And now, I'm bothered when something *is* on my mind that I haven't made a decision about. Sometimes I let it continue to bother me (hey, no one's is perfect) but most times I get it into "in" and know an action will be decided upon, and then done when the time is right. I began with "@Home," "@Office," and "Errands" and built a more complex system as my responsibilities grew--I didn't have to try to create a system that will capture all the NAs and projects that an upper-level manager with a spouse and children has. When I do reach that stage of my life, my GTD system will already be there.