• It is slow. If you've spent any amount of time using hprof, then you know what I'm talking about!
• You can't start and stop it at runtime. If you've ever tried to profile a web application with hprof, you know what I'm talking about!
• Filtering. hprof profiles everything and so it's slow and that output is expansive. When I'm profiling code, I want to know how my code is performing, not how some third party library is performing.

I like hprof -- it's helped me out more times that I can say, but it also has some short comings, which is why I developed JIP