I used it a couple of times, in HS my 4x800 relay team did the one week load thingy, dropped 10 seconds off our time (avg 2.5 seconds per each persons half mile leg, a pretty good drop) It basically super-hydrates your muscles, making sure they never run out of water, which is a good thing when doing intense training. It also has some other effects that are similar to a high meat diet, with out all the heavy digesting required. Only side effect though was cramps, doing 4 doses a day for a week kills off the natural bacteria in your stomach, which is your only source for a certain mineral (im thinking vitamin K?) that keeps your muscles loose, similar to potassium, but anyways, every muscle in my body was tight, and no amount of stretching could loosen them up, kind of annoying but i guess it was worth having that little boost in endurance. There is slight weight gain but is minimal, max 10 pounds per the avg person. Some weight lifters use it to gain permanent weight, but its not the creatine itself that makes you gain weight, it just makes it easier for your body to build/repair quicker.
Considering safety, there have been no documented cases where creatine has caused a bad side effect other than the temporary soreness i described above. There were a few cases in the news, such as the michigan wrestler who died while on Creatine, but they eventually blamed in on him not eating enough because he was cutting weight, and training too hard, the role creatine played in this is not fully known, but most people think it had no negative affect.
If your looking at weight gain, like most people are, Id say just do the one dose a day thing, if you want to do the one week load of 3-4 doses a day then go to 1 a day, thats fine too. But the results from creatine alone will do nothing other than make your muscles swell for about a week and get your hopes up. I suggest a diet high in protein from Chicken, beef and fish such as Tuna and Salmon, more than enough carbs, and a decent amount of fats and oils. Maybe a multi vitamin just to hit anything you might have missed. And a heavy lifting workout only 3 times a week, allowing at least a day of rest after each workout for your body to recover. You need to keep a constant supply of protein and carbs in your system, this means breaking away from the traditional 3 meals a day, or more likely your 1-2 meals a day, and eat 6 meals a day, evenly spaced from the time you wake up til the time you go to bed. If your not using creatine for weight gain/short term strenght/edurance gain, theres not much else its good for except now they say it has been shown to reverse the degenerative process of Lou-Gehrigs Disease.
Creatine is expensive, and truthfully it will only increase your success by about 10% max if used properly.
Check out MuscleGainTips.com, its a good site with a lot of info, they pretty much have a nuetral stance on Supplements. I recomend signing up for thier free newsletter.