I think the only way to know is to try it! I've been taking Bella for just over a year now and she absolutely loves it, barks her head off the whole way round with excitement and her tail never stops wagging.
When you first start there may be certain things your dog is a bit scared of doing - usually it seems to be the climbing obstacles, Bella was petrified on the A-frame to start with but fine with the dog walk, and she is still fairly dodgy on the seesaw but is a very brave girl and will go over it at a nice, steady pace.
It takes a good few weeks to teach them what to do, how to jump 3 or 4 jumps in a row, which sounds so easy but they often jump the first one then run around the rest to get to you, how to go through tunnels etc etc. You then hit a wall when the dog knows what to do and it's YOU having to do all the catching up learning directions, remembering the course routes etc.
I love it though, and I haven't entered any competitions yet but I just love running around with Bella and seeing her absolutely having the time of her life!
