In the demanding environment of my car on the M25, in the rare occasions I get up to speed, the headset fared well, and callers said my voice could be heard perfectly clearly. I also had no problems hearing the other party, but whether in the car or at home, the other person always sounding a little thing and distant. The headset behaved as I would expect, and pressing the button activated the voice dialling on my phone, which once set up worked well.
For sound quality the G5 does well then, and it's reasonable in the comfort stakes. Certainly its size is a big selling point, but really it's the charging carry case that's the really ingenious aspect. You can take that with you and know that you've got plenty of talk-time to play with and just charge it occasionally. Having it in the case means you'll be less likely to lose it, as otherwise it's almost too small. On one occasion I took it off when I got inside and put it into my pocket from where it accidentally got a ‘pocket press' and made a call, so you need to be careful on that front.
Overall, I have to say I prefer my old venerable Motorola HS-850 - yes it's a porker compared to the Invisio G5, but I prefer the way I can just leave the headset off and just flip it open and pop it over my ear when a call comes in. However, if you don't want a large flashing thing on your ear and don't have a problem with in-ear headphones, then the Nextlink Invisio G5 is recommended.
The Nexlink Invisio G5 is a Bluetooth headset with some nicely designed touches. The small size is a plus, the in-ear spring plug is clever and the charging case that extends talk-time to 20 hours makes for a stylish package. If you don't mind having an in-ear solution, this is a neat Bluetooth headset.