I am just finishing the 3 week primary fermentation of my first batch (Blonde ale), which never dipped below 73F. At it's peak, it even got to 79F and stayed there a couple of days (that's when I put it in the bathtub with water). Tonight I took my first taste with the hydro sample, and it was amazing. With ales, to me at least, it's safe to presume that the 70s are a safe temperature.
For future brews, though, I already have 1L water bottles (6 of them) that I'll be dropping in the tub for the first week on a daily basis, just to keep it more within range of optimal fermentation.