I'm actually not familiar with Jcink -- all my forum RP was waaaaaay back in the day during ezboard's day, or more recently a few years ago with Invisionfree, etc. (I ran a forum game I hosted on my own space before moving to IJ, but can't even recall what intermediary that used.) So tl;dr: is Jcink great? The free ones offer so many compatibility issues, in my experience, but I'm intrigued by the idea of build-your-own.
The IJ refusal to move, from what I've seen, seems to predominantly revolve around the loss of icons, and the inability to easily, recognizably comment-spam. Actual writing doesn't necessarily take the backseat, mind, but it also doesn't carry the predominant weight anymore.