Depends how they implemented midi and the timers. If it's win32 MIDI API stuff and Win32 timers the messaging isn't real time so you will get jitter. That's going to be worse on win vista and above due to a number of issues.

If it uses ASIO MIDI back end it'll miss all the problematic message loops.

I only use SYSEX and use the Triton Studio sequencer though as its the most awesome thing ever made by man.