The limitations are few, but still.. The ones which you might encounter when porting patches is the limited space for your interface (a "bar" instead of the optional whole screen), when dealing with midi specific patches you might have issues when using specific channels and such. However, that’s more of Live than M4L limitation.
Another one could be sending msp data from one patch to another. afaik that is also not possible.
But apart from that… It heavily depends on the patch, but I think most of them shouldn’t give (too) much trouble for porting.