We looked at the wireless units but the short battery life was a deal breaker for us. We ride brevets, starting distance of 200k, and are slow enough that we don't want to spend extra time at controls changing batteries.
It's my job as stoker to unplug from the unit as we are slowing to dismount. The captain keeps the small unit in his rear jersey pocket. Yes, I have forgotten once or twice. It's also easy to get the wires wrapped around a seat post or handlebar. And you need to use caution not to speak loudly to a fellow cyclists in the pace line while speaking directly into the microphone (ouch!)
I'd suggest anyone considering an intercom to buy it when it's priced under $20 to see if they like it before paying more. We haven't tried using it to listen to music or audio books (and I think it would even allow us to have a shared phone call on my iPhone). We use it just to communicate with each other. The earbud / mic arrangement is pretty inconspicuous - some people haven't noticed we are using it.
I'd be interested in hearing other people's experience with it.