I've heard ProGuard's Jar shrinker affects the performance of you application. Is this true? And if so just how much slower does the Jar go shrinked compared to unshrinked?
Actually, "shrinking" can only make an application load faster. Once loaded, there should be little or no difference in speed, though memory consumption can decrease.
Basically, the shrinker removes unused code, which reduces the amount of class-loading work the JVM has to do and the amount of memory taken up by that code.