Let me start this off by saying that I love this game. The graphics engine, and the mod/texture pack support are definitely better than what even Minecraft itself offers. I have a few suggestions though:
Please get rid of the mandatory V-Sync. It really does hurt my performance and the whole game would be better without it.
More graphics options. The draw distance is too low, and I can't change it, even though I wish I could.
I really do like what you're doing, and don't take these as demands. Just take them as suggestions.