Hi Boutchoo,
I have the Z77 Sabertooth and I do use those little fans. I know some people say they don't do anything for cooling, but I've tested having the fans disabled and then stressing the rig, then enabling the fans again and you can see a small drop in temps on the MoBo, Vcore and VCCIO. So based on that, I use them.
I have mine set up so the fan in the middle of the board is pushing air down under the thermal armor and the rear fan is pulling air out from under the armor and exhausting it out the back.
Hope this helps =)