Canya is 3, she's pretty good w/ all the other animals, although when she feels playful I've seen her chase them (the goats). Her temperment is great, she's easy to catch and handle, and takes things way better then the average horse of the same age.
A mule has to bond to you, then it's 'your' mule, which actually ran me into problems when I sent her away for training. She definately prefers me or my nephew, but now tolerates being handled by others. You can't 'make' a mule do something the way you can a horse, you have to convience a mule, and if they trust you they'll usually do it for you. They also have greater self preservation then a horse (they don't do things that will get them hurt).
I've been told john mules tend not to mature as quickly (mentally) as mollies, and the majority of the mule people I have met prefer the mollies, and w/ my limited experience I agree!