This is one of the best-kept secrets in the M42 manual focus field. Instead of spending $300-400 on the Canon nifty-fifty 1.4, I probably should've picked up one of these years ago when I started shooting digital. I acquired this solid aluminum gem a few months on Ebay from a Ukrainian seller for about $35 total. I am still looking into getting another one in case this one gets crushed or dropped by accident. As you can tell from my previous posting in which this lense was mated with my GF3, the colors and bokkeh are spetacular and it is sharp wide open.
It stays on my T1i almost permanently, as the metal dial is wonderful for candid video. Most of these sold on Ebay come without lense covers, but this is easily solved. I bought a camcorder adapter ring and lense cap for the front. You just can't build quality like this anymore; even the plastic 50 from Canon will set you back $80, which is more than double the cost of this lense.
If I had a T3i with the flip-out LCD, this would be the perfect low-profile street cam. The Industar makes the rebel look like a non-threatening bridge camera.