Microphone quality: 5/5 - Excellent. Tested on Skype, Teamspeak and Ventrilo. 100% of people from Belgium, Sweden, UK, Scotland, France, Norway and Denmark all said that my voice was crystal clear. No feedback, no echoes etc.
Sound quality: 4.9/5 - excellent. On every program tested, I could hear every voice as if they were on a very very clear phone line to me. On 1 instance out of 20 there was VERY slight fuzziness far in the background, but on testing we're pretty sure that was the network and not the earpiece.
Fit: 4.5/5 - Very Good. I personally hate in-the-ear headphones, so was wary about this. Wearing it for 1 hour however, there was no pain. Note you DON'T need to shove this into your ear canal, so there shouldn't be any issue. It rests on your ear, and you rotate the plastic hook so that that rests on your ear. IF this was for "out and about" as a bluetooth headset, it wouldn't be perfect - however this is not for on the go, it's to be used on a PC or Laptop. Not once did I have to readjust or move it.
Build: 4.5/5 - Very Good. I am a little worried about the earhook, but, it IS very solid, and if it does break, it will be my fault it broke.
Price: 5/5 - Excellent. I would easily pay up to 15pounds for this. I am actually buying another one for my wife.
NB: The poor reviews below seem to stem from personal errors that caused damage to the product. Personally I don't see this as a reason to criticise. If I buy a car and drive it into a tree, it doesn't make the car a bad one.