Funny you should post a thread like this, because I've only been thinking recently about whether my life would have been any different without drug use.
I don't think I'd change anything - I've had mostly good times when it comes to drugs. Whether those experiences would have been any better or worse without, who knows. There's probably a few occasions where I would have been better of sticking to my guns and not having anything, but hey... you live, you learn.
I was 20 when I first tried pills, but was nearly 22 before I started using anything on a regular basis - wouldn't want to have done it any earlier than that.
Without drugs, I doubt I would have come across this site and that's probably had a greater impact on my life over the last few years than drug use itself.