I became aware of Spax screws a few years ago and even inquired in this forum if anyone had used them with no success. I recently became aware that they were available in Oz so I cleared the moths out of the wallet and bought some of the MDF type.
The reason I became interested in them originally was the drive system, they use a Torx drive system with a centre spiggot to locate the driver and I thought it should be a good system. I have used all types of screw drives including a very large number of square drive and I wanted to compare with what I knew already.
I have just come in from the workshop after using them for the first time and all I can say is WOW. They have a very sharp flute on the end of the screw which drills into the material thus negating pre-drilling with a serrated thread form to cut the material as they go in and the underside of the head has a cutting action as well to form the counter sink. In my view square drive is good, a major leap over phillips but these are better than square drive by the same margin. I ran some of them into hardwood and they just kept on going below the surface with no sign of stopping.
Highly recommended.
SPAX Screws Australia Stainless steel screws for timber & decking
Usual disclaimers, no connection with the seller etc.
Spax Screws 
