I'm rewriting one of my apps in Swift and I'm enjoying it a lot, but it's definitely a bumpy road. You're dealing with both a beta IDE and a beta language, and you have to get used to a myriad of errors, some of which are indecipherable (arcane things like issues iterating over an array or Optional behavior that doesn't mesh with documentation/templates). Still, Swift is a joy to program in compared to Objective-C (at least IMHO) and its giving me the chance to re-architect a very poorly planned v1.0, so that alone is worth the trouble.
I think it's a good idea if you're very interested in learning Swift, but not really worth doing for its own sake.