I've been taking collagen peptides, one scoop a day, for 3 months now. My joints are in much less distress due to my active lifestyle, my shoulder problems have nearly disappeared (though I don't expect it to ever fully be great until I stop paddling), and I generally feel good overall. What is really different is my hair, nails, and skin:
Hair is growing insanely fast. How do I know this? Because I touch up my roots to cover grays, which I needed to do every 4 weeks (exactly) and now have to do it between 2 and 3 weeks. That is INSANE. There is also much more new hair that is now very noticeable, which I mentioned earlier. Also insane.
Nails are growing equally quickly and are strong, but they always were strong. Still, super fast growth compared to before.
And finally, fact: my skin is far more hydrated than it was pre-collagen. This is nice, because it seriously used to flake and be grumpy even in the tropics. I still have fine lines and wrinkles thanks to smiling ...but my skin somehow seems more thick and the lines aren't as obvious? Under no circumstances do I believe they will go away (not going to stop smiling), but this has been a neat benefit.