I've been working on mine for the last 4 months or so. The turn based system was kinda tricky, but it seems to work okay. I've had to be creative to solve a few problems here and there, but I'm happy with the way things are going. I hope to be able to show it off in a month or so once I get some more graphics done.
I'm working on an item shop RPG and there's a turn based trading system... It's been difficult to figure out but a lot of fun. I'll keep an eye on this thread and maybe post some of my own ideas sometime.