Similar in the way that Gingerbread is similar to Eclair. One is the decedent of the other but improved and changed. Some of the core functions will be different just as Eclair and Gingerbread are different. The way things are currently shaping up it looks like Honeycomb is going to be the oddball OS. ICS will take the better Honeycomb features and evolve Gingerbread is how I would describe it given what I have seen so far. Really though ICS is a leap forward so comparing it to what is already available isn't so easy.