They aren't nearly as flat as most "studio headphones" so I wouldn't necessarily advocate them for mixing, and it goes without saying that while positioning a mic you're either going to want to use something else or, preferable, record a couple seconds of a "test" clip once you think you've got your mic position sussed out and listen to the playback on your monitors.
But, on the plus side, they have phenomenal isolation, both for external sounds bleeding in, and for the playback bleeding out. Even on a very sensitive mic running pretty hot recording acoustic guitars, I was getting zero bleed while monitoring bass and drums at a pretty comfortable, not-quiet level. These things are more silent, from the perspective of the microphone, than any "proper" headphones I've ever worked with, and block out a ton of external noise, too.
It just feels weird working with something as small and light as in-ear buds. :lol: That said, I'll be buying a second pair so I don't have to grab them off my iPod whenever I want to track.
For those of you more experienced than me, is there anything I'm not thinking of where I would NOT want to use in-ear buds in a studio setting?