All my dogs work and I tried agility with Tilly and Alfie a while back just to see if they might like it. Tilly hated it, she thought it was utterly pointless and hated all the dogs barking and getting worked up around her; I took her twice and then didn't inflict it on her again after she all but shut down completely the second time. Alfie was quite good at it, he's very fast and athletic, but it didn't get him going or focus him the way working does, the bit at agility he got most excited about was when I got out a tennis ball to use as a reward and he was more excited about the prospect of getting to retrieve it than doing any of the agility stuff. He was fixated on the ball and the jumps and stuff were just incidental
I completed the beginner's course with him but didn't take it any further than that.
I've never tried it with Rodaidh, it would have been impossible last year with him having had an operation on his leg shortly after turning 1 but I don't think I would anyway, he doesn't do so well with lots of other dogs going nuts in close proximity around him, he's much better on shoots where the dogs are all quiet and although they're all enthusiastic about what they're doing they're all getting on with the job at hand.
All that said, I quite enjoyed the agility myself, it was a good laugh and if I ever get a dog who I'm not going to work and who I think would like it I'd definitely give it a shot again.