Save game and new shaders would indeed be nice :)
I wouldn't say the latest improvements are minor details though. Interface tweaks may seem minor, but given the fact RPG in a Box aims to be very accessible and easy to use, this will make a difference on Steam. But of course, given the primary focus of the engine on the RPG genre, it will make sense to put a high priority on more RPG-related mechanics and features. I'm also looking forward to such features, not for my current projects, but for a possible third one... Anyway, I think Justin has been doing some amazing work :)