I put some Schwalbe Marathons (26x1.5) on my Cannondale F900 for my commute about 1 and a half years ago. And not one flat. So I am happy. But, it could be that the roads here are in good condition and regularly sweeped. I didn't have much of a flat problem with other tires, but did have flats.

They are heavy, and a bugger to get on the rims though. Speed is so so... I am looking at the Marathon Racers for my next set. I hear that they are a little lighter.