Unless you have a data plan with less than 2GB of data, that is. And are OK with waiting a bit for things to buffer. With Google Music I end up offlining a lot of songs because data plans in Canada are terrible and because 3G isn't everywhere you want to listen to music. Add podcasts and you hit the storage limit in no time.

I live in New York; most of the stations and tunnels have no connectivity whatsoever. If I want to listen to my music offline, I do have to sync it.