I bought the Q2 back last winter and was fortunate enough to be able to trade up to a G4 Team Set before I even had the Q2 on the bike. Didn't like the Q2 just when trying it on the couch.
Cousin and I each have the G4 and I use mine connected to an iphone 3 and then more recently the iphone 4. Very please with the system....
- Battery seems to go for ever, 12 hours listening to music, some intercom and some phone calls and still ticking. I tend to plug my in when I'm not wearing the helmet, but even when I forget over multiple days, I've never seen the battery go dead.
- Intercom - Have had conversations at 90+ mph. But full face helmet needs to be down or windshield full up. It has noise cancellation, so you can't hear the bike or wind unless the mike sitting right out in the wind.
- GPS - can connect, but I don't have a GPS with bluetooth.
- FM Stereo - pretty much a waste, probably better if you were in a big city with stronger stations.
- Cell Phone - Again noise cancellation does the job. Have had several calls at 60, but over that too much noise and not in my comfort zone.
- Stereo - My main use of the set, I find great. Originally with iphone 3, you couldn't control the volume when using AD2P so music was too loud. This was resolved in an iphone 3 upgrade, but still could not advanced through songs. Advancing through songs was solved with the iphone 4. So AD2P works just as expected, great quality, plenty of volume to make you go deaf.
- Biggest problem is learning to just let the system do it's job and remember when to and not to press buttons. For example when a phone call ends and you want it to go back to music, just leave it alone it will go back to music. If you get impatient and press the button to turn on music, you've actually just turned it off, because it was already on, just muted.
- Also find, that I turn off the voice activation. I sometimes sing to the music and with voice activiation I've ended up singing to my cousin on his bike or singing to an incoming caller.
- I have the boom mike mounted in a full facs HJC IS16, but there is room between my mouth and chin bar. I didn't like the foam on the mic hitting my lips so I just left it off so mike is only about 5 mm thick and never touch it. They do have a flexible wired mic that you can swap with it. And Schuberth has recently incorporated the G4 into an attachment specific to their helmets that looks some what like an extension to the helmet collar.