My smash bier (US 2row, German Tradition Hops, Notty yeast) turned out excellent. I even missed my mash in temp initially as it was @ 146. I added enough boiling water to raise it to 151.6 and it went well from there. I've had fairly poor results with trying to mash anything above 153... but then again that could just be me. While the science says a higher mash temp is the way to go, my smash had a fg of 1.008 and was very drinkable.
Ps I used my smash bier brewing session as a way to relax while brewing, as I'm usually VERY uptight about everything being JUST RIGHT!