I have two ST1's, as I ride along with my son (on another bike) often in the summer. I needed to buy two communication systems and could not bear to pony up over $1000 to do so.
What's good:
They are small, light, battery powered and will run for a very long time on a pair of AA batteries. No need to wire into the bike. Seriously, I have over 150 hours on a single pair of alkaline batteries and still no sign they need to be replaced. THey come complete with 2 headsets and with just about every adapter /cable you could need to your run driver / passenger intercom, input music, a cell phone, a GPS, and hook up a bike to bike radio (FRS/GMRS).
I have made phone calls over my Moto Razor while riding and the other party could not tell I was on a motorcycle.
They are inexpensive compared to the competition.
What's not so good:
The audio is binaural monophonic (ie not stereo). This is really too bad as the ear speakers are wired seperately and could easily have been made stereo.
The amplification (volume) is not adjustable except that you can vary the volume out of the input device. This works OK, but is not optimal. You cannot fade the audio between rider and passenger, so if only one of you is wearing earplugs you're screwed.
The amplitude of sound, and the quality of the sound at full amplitude, is barely acceptable if you wear high attenuation earplugs. I like to wear the 33dB attenuation orange foam earplugs as they are the most comfortable and do the best job in my jumbo ear canals. With these plugs in I need to run the input volume rather high and I feel I am over driving the amplifiers in the ST1 as there is some distortion of the audio at times.
