I've had a light weight-lifting routine for a number of years, now. It's the way I stop from becoming an absolute porker as I pursue my hilariously opposed life as a gourmet. I started taking creatine not as a physical supplement, but for its cognitive benefits. With even a small dose, increases in memory and processing speeds have been noticed. I'm always after ways to give myself an advantage in... in... whatever the hell it is I do that requires an advantage (Got it, Street Fighter IV!), so after hearing that Creatine is actually pretty well-supported experimentally, I was on Amazon with my credit card out.
But holy crap, I noticed quite an increase in my weight-lifting stamina. I've gone off and on Creatine multiple times to make sure that it's not in my head, and I feel highly confident that it is a real effect. It has no effect on how much I can lift, nor does it affect my ability to handle weight and cardio without tuckering out completely, but if I slowly work my muscles, I can do significantly more repetitions per set.
Without creatine, it is difficult to impossible to do three sets of ten reps of a tricep lift with a 30-pound weight in each hand. With creatine, I can do three sets of twelve reps with more in reserve. I'll frequently do fifteen or sixteen reps on my final set. It's very impressive.
Side effects? After not taking any for a few days, then taking a decent dose, I fart... a lot. Combined with my hilarious doses of Fibersure, I fart even more. My urine is also incredibly odoriferous. I can't describe the smell. It's just... a smell. And holy crap is it a smell. It dissipates quickly, but it's strong as hell.
I haven't encountered any other side effects. My dose isn't high enough where I'm bloating. My muscles don't look any bigger, which is a big goal of many body builders. And since I drink a lot of water anyhow, I haven't encountered issues with dehydration.
Considering the cognitive benefits, I recommend creatine to anyone. The studies show no nasty side-effects, and if the only notable result from extended usage is smelly pee, I think it's pure gold.