Pete,
It's a HW Justock -
http://www.hobbywing.com/product_show.asp?id=250
Works fine on 1S with no booster
The only 'trouble' i've experianced is on track designs that have really sharp, sudden switch backs and more than one very close together. You can sometimes get a 'judder'. I fitted a Cap and it sorted that problem out. Just helped it get back out from dead stops.