I maintain my company's in-house mobile app crash reporting system and I had to remove jailbreak checks from our iOS SDK. It turned out that some of the checks were causing crashes themselves due to buggy anti-jailbreak-detection code some jailbroken devices had in place. e.g. checking whether a file could be accessed that normally iOS disallows would end up causing a crash instead of just a permission error.

Instead, I just do some basic server-side detection. Basically, looking for libraries loaded into the app (e.g. cydia) that are only present on jailbroken devices. Some jailbreaks don't even try to hide their presence.

I don't know what iVerify does. I hadn't heard of it before. I'm curious how it avoids crashes though... perhaps it avoids invoking any dynamic system calls.