Only prob I’ve had with different midi devices is their performance. For example I found that when I plugged in a firewire M-Audio Profire it introduced a really long delay in chasing midi program changes, whereas my Midex8 seemed to have no delay but didn’t always chase correctly… So you may find some interfaces are better than others, but otherwise, as said, they all cooperate together. I currently use 3 different midi interfaces to connect to hardware synths plus 2 USB midi external hardware synths and 1 USB midi keyboard controller.
Mike.