I've been using Switch Grips for over 2 years, maybe 3, and so far, I've only had one slug crack on me. The bottom "wing" on the insert cracked and it was fixed with super glue, which held for about another 2 months before I had to replace it. I have Em in all my balls now and just got the system installed in a couple of my 14 year old sons 15# balls. In fact, now that he is throwing the same weight as me and has the same span, he can now throw my balls, which now saves me some money for now.
I know it sounds like I'm in denial, but I'm not.