Actually, all my best RPing experiences happened on MSN Messenger/Yahoo Messenger with my inner circle when we were using my main story project setting, basically once forum RPing seemed to fall into large decline and the forums we were using stopped having activity. So while I started text-based role-playing on forums, my best experiences technically came outside of them.

Now that decent IM programs have pretty much fallen into decline, I'm in the process of creating a new forum using my setting in the hopes to breathe life back into that kind of quality RPing.

My worst RPing experiences mostly came from trying to write using settings that weren't my own, since my passion for writing is largely rooted in my passion for my main project, and I usually end up having to severely dumb down or alter my concepts for them to fit elsewhere.