The reviews are mixed, as is the case w/ a lot of FSU gear. I imagine that if you get a good one you're in the gold, and if you get one that's been taken apart and put back together sub optimally, you won't have much. Some of these are on long mounts too, which is going to have an effect on achieving focus w/o burying the lens into the print. By the by, KEH had an El Niikkor 50 2.8 listed for $23 the last time that I looked. That would be a smarter move.
My personal experience w/ FSU camera lenses has been stellar. Great glass. I don't see why it would be any different on the enlarging lenses except for that pesky QC thing. My experience w/ the cameras has been the exact opposite, and I won't have one if you give it to me. Don't forget, if you don't get a good copy of a lens, sending it back would be so expensive as to be impractical. So if you buy one, buy one in your country. Just in case.