I love juggling kettlebell!
A couple of years ago I worked on the levels from Logan Christopher's ranking system and got up Level 2, which is the second highest rank.
I originally got into it just because it looked like a fun way to do some conditioning work, but I found it provided a few additional benefits as well like increase grip strength, power and improved hand-eye coordination.
I never got any injuries and I actually think juggling done properly may help prevent injuries because of the forces applied