The slot loads also can't play those funky mini or business card cd/dvd's. But they do look cool (for example: the mac cube slot load implementation). About negative air-pressure, I doubt you'd have as much opportunity for dust to run through your slot load drive, then into the case, as you would for dust to come in through the numerous other cracks and crevices that run directly into your case. For example: the space above and below drives, little spaces between slot covers (on the front and the back), etc. Your best bet is just to have more air blowing in through fans than blowing out, then you have dusty air in your case, but no dust in the crevices... Or you could put filters on your fans AND have positive pressure and have a really clean case.