That just about covers it. With the DM-4 & DM-5 any momentary switch will do the job (keyboard sustain pedal). Tapping the petal will create the closing hat sound, striking the trigger with the switch depressed will give you a closed hit sound, and pedal not depressed will be open hit sound. There's no velocity on the pedal stroke and no continuous midi controller signal for that high-hat half closed splash effect. The Dm-Pro supports this (even triggers cymbals clattering after a quick close/open punch on the pedal).
I've got the DM-5 and the Pro. If you're a drummer you may want to consider the Pro... You might get frustrated with the triggering on the DM-4 & 5. The Pro handles the triggers a lot more gracefully than either of these two. I was never able to get the 5 set up so that I wasn't either missing or doubling triggers. The Pro took me a few hours and was perfect. The 4 or 5 is a good sound module to drive with midi, or to punch up some recorded drums that just don't cut it. I'd go with the Pro if you're going to drive it with triggers (especially if your triggering an acoustic drum kit, those are much tougher than trigger pads to set up).
Steve