Nothing in details available.  I attempted to load my pre8 world (which was started in pre2 or pre3) and it crashed kicking me back to the launcher just stating Minecraft has crashed.  I thought maybe this was an issue with the world and attempted to make a new world and it also crashed.  In both cases I was attempting to make a floating isles map. I wish I had more information but that is all.  Sorry. Not that this is the place to suggest things, so take it as you want or not.  I miss the ability to choose at what levels ores spawn.  In Floating Isles this seems important.  Also selecting multiple biomes would be great.  It seems too bad to have Floating Isles in only one biome. That's all.  Thank you for being so dedicated to a great game.  I appreciate it more than you can know.  Thank you.