Dave Ramshead used one to score a 80ex80 at the Gathering and I shall be using one next year.
I reviewed one for Airgunner last month and I love it.
I can email you a copy of the review if you would like.
Somehow I made TEAM ENGLAND 2012 and 2013
Illiterate writer for AirGunner
The real Kung Foo Panda.