It all depends on your ears. If you’re one of those nuts that say that anything less than 320kbps is murder on the music, I feel for you. Personally, I have ears that, while sensitive, adapt very quickly to the quality of the music. A 160kbps mp3 sounds perfectly fine to me. I can juuuust hear the slightest quality loss in 128kbps mp3s, but I don’t notice it if I don’t look for it, and it’s so small it doesn’t bother me anyway.
I’ve also transcoded my whole music collection to (horror!) quality 2 Ogg Vorbis (average of 96 kbps) and it still sounds perfectly fine to me.
While there are golden-eared audiophiles that may even be able to hear the difference between a 320kpbs mp3 and a 192kbps one (and if you think you can, I encourage you to try blind testing), for the vast majority of people a 128-to-192 mp3 will be fine, and that’s why people buy (or, most often, download) music in mp3 format.
I’d just wish the world switched to ogg.