I bought a Bluetrek G2 initially to use with my T-mobile Vario, and unfortunately I was dissappointed. For all its benefits (small, light, excellent battery), even though I can hear people very well, people on the other end say I sound as if I am speaking through a tunnel... muffled.
I was reading excellent reviews about the new Plantronics Discovery 640 and decided to give that a shot. Wow... what a difference!!!!!... The voice quality is excellent!!!! The funny thing is, people can hear me BETTER when I speak through the Plantronics than speaking without a Headset. Plus I can hear them very well, loud and clear. I actually don't even have the volume to max because it's too high...
Other benefits include the fact that it is small, I wear it without a loop around my ear, and it's only 9grams. Very concenient to just carry in your pocket. It also comes with a nice case, adapters for various phones, and even a charger on the go that uses AAA to recharge your headset.
The battery is supposedly not as good as the Bluetrek G2, but who cares? I get through a whole day (sometimes two) without issues, and I charge it at night alongside my phone. I use this headset for my phone, as well as Skype, it's so small and light you forget you are wearing it.
Only disadvantage that I've found is that the range is not as advertised. I can walk about 5m away from the phone without issues, more than that I get deterioration. Plus, if I put my phone on the "wrong" side of my body (phone on the left, headset on the right) I get static... But I can live with that, just a minor inconvenience.
So there you go. It's a bit more expensive, but you do get what you pay for. Better get the right headset first time around, rather than pay twice like I did :)