Depending on style, I mash anywhere from 149 to 152. I think I did 154 once, but don't remember the style.
Anyway, at a recent non-bjcp competition that was judged by the brewer and owner of a local microbrewery, it was suggested that I mash at 160, or even a bit higher. Traditionally, I start freaking out if I get to 155 or so. The two beers I entered were a Session IPA and an Imperial Stout. The same brewer made the statement "crystal malts are the enemy of good beer"
FWIW, this is my favorite brewery in the Seattle area. (Fremont Brewing)