Nike streak 6. I love the way the shoe feels and it feels like it would be a good marathon racer, but the sides on these rip very quickly. By 150-200 miles, the side is so ripped my foot is coming out. I like to train in the shoes I'm going to race in, so these can't work for me because I can't afford new shoes every 3 weeks! Usually when they rip, the soles are still in great condition, which is a shame.
A runner up is the nike streak lt 3 and 4. They rip in the same way as the streak 6, but not quite as soon soon. I can get over 350 miles on the streak lt 3 sometimes. I wear these for all my training (almost) because they can usually be bought on sell on running warehouse whenever nike releases a new color. I'd use a different shoe if these didn't have the perfect fit, they feel so amazing on my feet. The streak lt 1 and 2, xc 3, and xc 2 used to have the sole wear out on the forefoot before the upper ripped, but the lt 3 usually has the upper rip well before the sole is trashed.
I actually like the streak 6 sole better than the lt 3. I wish I could get a streak 6 sole on an lt 3 made with better materials. Nike has to have the technology to make an upper that doesn't get trashed so quickly. Or maybe its intentional to save a tenth or two of an ounce, which if so it isn't worth it.