As far as I've seen, a few minor clarifications added to the rule book (which are also in the original CC:M anyhow), and the cards are stiffer in the newer release. They'll probably last longer but are harder to shuffle.
Sleeve the cards. The originals "chipped" easily and needed to be sleeved both to thwart wear and to protect from "marking". Regardless of version, sleeve them. If you get an early copy, download the current rule set - the differences are small.