Let me fire up this discussion a bit!
Here's an article I read on the velonews website: http://www.velonews.com/tech/report/art ... 970.0.html
Apparently at Geax and at Intense Tires research has shown that tubeless systems with latex and regular tires are less efficient than true UST tires. Sidewalls of regular (racing) tires are designed to be supported by an inner tube. Without the inner tube, these tires transfer less force from the rider to the ground they say. Makes kind of sense to me!
True: Eclipse, Stan's have less rolling resistance, but apparently there's more to it... I am a latex solution fan myself, but this one is worth the read!
Just a thought: If this is true, a UST rear tire and Stan's/Eclipse front tire would be the way to go! (The force generated by the rider is only transferred through the rear wheel)