I have a Rider TT bike and it has been awesome for 5 years and still going strong. I know lots of people in Memphis ride his frames on the road and off-road and the bikes have a great reputation among the elite athletes in the area. One athlete won the junior (16-18) national Triathlon championship this year, 2013, on a Rider frame.
I am suspicious about a bike shop employee putting down another brand. 1) he is biased. 2) he would get employee discount on any brand carried by the store (about 1/2 price) from the brand so it is unlikely he would purchase a bike from anywhere else. 3) I asked around and have not heard of anyone breaking a Rider Mt. bike before.