I especially like them for commuting because I used to start before sunrise, and the photochromic ones were light enough to ride at night, and dark enough to cut the glare during the day. Keep in mind they're never as light as clear lenses and never as dark as dedicated sunglasses, but a very good compromise.

Performance has some decent photochromic sunglasses for $40 (Scattante Team PCL). I have a pair of them and they work fine, although the nose slips a little on my super sweaty face. Tifosi has an assortment of them at the $60 mark.