I had restlyane injections for tear trough hollows a few months ago. It's definitely the kind of subtle change I'm looking for as I'm only 31 - I don't want to look too plumped up or plastic. The dark circles are greatly diminshed and I think it gives me a refreshed look.
Due to the site of injection (under eyes), I did experience a bit of swelling and bruising. It was nothing extreme or embarassing, but if you don't want someone to ask you --"oh, what happened?!", then maybe lie low for a couple days. Otherwise, I've noticed no side effects and now I'm just curious as to how long it lasts.
My advice is to DEFINITELY find someone qualified and competent w/ these injections. I can see how this could go horribly wrong. Don't just let anyone mess with your face and find a facial plastic surgeon!