Like [soundwave] said, you'll have some dust inside a Detolf, but much, much less that having them on regular shelves. I have them in a room where I'm in often (Computer, TV for watching movies and video games), and there's a lot of dust buildup as a result. But in the Detolf I've yet to dust the toys or shelves, no sign of any apparant buildup of dust in there! Comparatively, my loose toys outside the Detolf are midly dusty now, should be due for a cleaning soon.

So it's safe to say that despite the gap around the door, you'll save yourself a lot of time on dusting stuff!

 

Hmm, what if I were to seal the openings on the side? I live in the high desert, it's beyond dusty up here.