My viewpoint is that it depends on the base malt you use, to a point. British malts work well for a single infusion at the 148-152F range. The modern connitnental malts work in that range or do well in a step mash. The North American malts with very high diastatic power work well at the higher temps.
Sierra Nevada uses NA malts and mashes around 158F IIRC. What do you remember Denny?