I've fixed many of the crashes from the last build. When you're using multiple threads to do different things (rendering, simulation, input, etc), you need to be extra careful to synchronize data access. Writing to the same memory location from two CPU cores at the same time is bad. But there's a fine line between synchronizing too little (and crash) and synchronizing too much (and deadlock). Short story, I think I've fixed most cases, but if you see crashes or freezes, report here and I'll fix.
Also, on iOS the lo-res graphics issues has been fixed.