I've been clicker training Kona (now 2 years plus) since he was about five months old. In *his* opinion, the day is not a good one unless it involves "training time."
Kona is our office kitty (we have clients who specifically come by just to see him--we're hoping that adds to our financial bottom line someday, too, LOL) and we've found he is just a happier cat--and more settled--when he has his training. We also believe that the wild kitten stage was mitigated somewhat with the clicker training--he's such a *smart* cat that I think working his mind to figure out the "behaviors" we set out for him truly helped to calm him and focus his actions in a more positive way (not that we didn't have several blips along the way!). And, the previous poster is correct, while the initial food feedback (we use dehydrated chicken:
http://www.amazon.com/PureBites-Chicken ... 96WD5MQDKX) was what Kona wanted, it quickly evolved into just enjoying the one-on-one attention from me and the chance to work his mind in a different way.
If you're even *thinking* of clicker training, I'd suggest this Yahoo group:
https://groups.yahoo.com/neo/groups/cat-clicker/infoIt's filled with folks who clicker train for various reasons (fun, agility coursework, socialization of shelter cats) and they have lots of folks who post regularly with very practical tips. There are also a series of documents on different behaviors, the science behind clicker training and training pitfalls to watch for.
We don't have a "circus cat" in Kona (although I confess I did find a small hoop at the 99-Cent Store and he loves to jump through it), but we do have a much happier cat who also has many ways to "interact" and impress our office visitors--and he loves the attention it elicits!