bought this for road cycling across the north york moors during winter under helmet so wanted something light and thin. got this and no regrets, it's light, comfortable under helmet don't know it's there, warm enough and amazingly never gets soaked in sweat, it works and stays dry. would recommend it for all cyclists but walkers may want something thicker/warmer.
update 9/1/13 - not warm enough once temp <8'ish degree celcius but fine upto 12/13 after which i don't use one. also wears really well after numerous washes.