Went to YoYo's awhile back. I wasn't blown away by the experience. Self-serve yogurt is a tricky thing, because it's left to the customer to experiment flavour combinations on your own. This is ok, if the toppings were fresh and if the yogurt was good.
Problem at YoYo's was that there were too many flavours and too many toppings. The yogurt was kind of melty and not that tasty. Then adding the toppings, in combination - no flavour stands out at all.
It's also more expensive then other self-serve yogurts that I've had. Given how much a yogurt cup can cost,, I prefer going to a fro-yo place where sized and pulled for you, and the toppings are fresher.