i took some for three years alomst a decade ago, non stop and started having porblems when urinating, pain, creatinine or something, felt like small stones in the uretrha....horrible sensation, was scared to go pee, read some stuff about it on the internet and stopped taking it and the pain stopped too after two weeks to my relief. It definitely causes troubles to your kidneys over time. For me, it took three years to start having side effects.
it obviously gives you more strenght and lots of water retention. Weeks after you stopped , once all the extra creatine gets off your body you start pissing away all the water and you get smaller. The muscles built by the increase in strenght and stamina stay tho. But you cant train as hard as you did when off so it also eventually decrease after some time.