Pen expers is an extreme version of a very common theme in electronic music -- having a slow reflective melody play over top of an abrasive rhythm section. This can be seen in Vordhosbn by aphex twin, the siege of antioch by Paradinas, tundra 4 by squarepusher, ect ect.
But something about Pen expers makes it so unique. Maybe it is the simplicity of the 6 bar chord progression (which is all the melody is, actually), maybe it is complexity of the drums. It's probably a mixture. Everything just werks perfectly. It throws this wild frenzy of a drum beat at you, and then offers you a distanced perspective to look at it from. This is the pinnacle of reflection expressed with sound.
Edit: fixt theme (I spelled it 'them' before)