As for the 50mm f/1.0, I don't understand why it sells for so much money. It has ~1/2 a stop advantage, but reviews say it doesn't perform well optically at any aperture, and if it sold well to begin with, Canon would have continued producing it.
[Yet, I think I'll keep my EF 15mm f/2.8 FE after I buy the EF 8-15mm f/4 - I like that lens]
I have to agree with you on the 50mm f/1.0. The 15mm f/2.8 fish-eye is a real keeper however.
Zeiss Ikon Contax II, Sonnar 50mm f/2, Sonnar 135mm f/4