Colyn,
Interesting that you mention the Summitar because I have recently been looking at those...
I know there are lots of 50mm lenses that are better in several different objective ways than the J-8; newer, better coatings, better build, etc., but I still am very happy with the results I get from my J-8. The Summitar falls into that area a bit, I think (well, except for build quality--it is far better than the J-8 I bet!); archaic design but still very capable.
But let's not talk too positively about that lens or the prices will rise! 😀
Rob