The other advice that I would give you is that before you do so, take a deep reflective look at yourself and ask, am I the type of person that likes learning new things, as well ask yourself if that will remain true as you grow older. If the answer is no, then be careful about chasing the hot technology path, because it requires constant retooling. While Ruby, JavaScript and Objective-C are hot right now in 2 years it may be Clojure, Dart and Go. You have to be prepared to retool as soon as the market starts to trend away from the currently hot technologies. There is also a trick to not jumping too soon and not waiting until everyone else has jumped on the bandwagon. Playing the cutting edge game takes a certain type of person.

If you get lucks and land in a start-up that succeeds, then the issue is less relevant, but until you do land with a success story you have to plan like your next job will be in a totally different technology stack, because it may be.