| Can't see it being illegal or considered dangerous by insurers. Autocom actively market the ability to use MP3 / SatNav etc with their systems. I've also seen several bluetooth solutions recently that support phones too.
Personally I've never got on with cheap earbuds whilst riding, but now I've got a set of etymotics I'll possibly try again on longer rides (when it's warmer), especially with their noise elimination benefits.
Other than comfort of the earbuds, noise cancellation, bass reproduction and volume restriction would be where I'd be most concerned.
No less distracting than Rage against the Machine full chat in the car.... | 
Hybrid Mode
