Yes, they are. Although in my experience, the Minolta 28mm M-mount is pretty soft wide open. The 40mm Summicron is superb, and left an unfilled niche that C-V has again filled with the 40mm f:1.4 Nokton. The test shots I've seen show that to be an excellent lens as well.
Originally Posted by Flotsam
As far as less expensive, I don't know the Russian lenses from experience. The Cosina-Voigtlander 35mm f:2.5 "classic" and their 28mm f:3.5 get excellent reviews, and can be had new for between US$225 and US$290, about the same as a used 40mm Summicron. There's also an estimation focus C-V 25mm f:4 right in that price range with unique click stops at three distances so that you can focus by feel. You can find the C-V lenses used as well, but they seem to hold their value. They're also not speed demons, so not suited for extensive low light shooting.