I'm scratching my head, and the only 'important' things I can really think of that are missing are GUIs and.. Particle Systems. (That last one must be a tough nut to crack

Those two aside, I really can't find anything that is lacking.. Maybe LODs and other optimizations? BSP? Some advanced physics stuff like subworlds?
(Not too long ago there were polls to prioritize the upcoming features and now I'm scratching my head just to find anything that hasn't been implemented yet..
