If you're using them with your iPhone 3G(S) they're great, of course the skip forward/back buttons don't work with the iPhone. The sound is really good for the average user (Good bass range) The talk features are adequate what I'd expect from a bluetooth headset without noise canceling tech in it.
My one issue was when I paired it with my MacBook Pro 15" (Late 2008) the sound was crackly and buzzing, like a broken speaker. This was very disappointing. I checked that my audio out settings were correct. I had selected stereo bluetooth & there's really nothing to change on the Mac. I don't know if this was a glitch in my software or the bluetooth hardware in my Mac, but if this is normal it's kind of a dealbreaker for the cost. The Motorokr S305 has a higher rating on the Apple website and more reviews than the MM100. I read through those and my opinion is save your money and go with the S305 instead. It's practically the same product at less than 1/2 the price.