I have noticed some issues with modules that use midi. I have been unsure if the problems I see are baked into Java, VM, or if they are the result of the modules themselves. I would like to believe the problems are not baked into Java or VM, so I hope you are right.
At first I was inclined to suspect that coders/module makers who do Audio/DSP treated midi as an afterthought and therefore weren't as diligent with their midi processing.
I have started exploring the use of VMD in order to decide for myself if the kinds of midi processing I have done before and am interested in doing within VM is possible. Based on results from a very simple midi tool I have started to develop, the problems I have seen might well be a combination of all three (Java, VM, and module makers) to varying degrees.