Distortion: none that i'm aware (no rigorous test).
Flare: none that i had noticed so far.
Sharpness: perfect even wide open. Just a bit of CA and lower contrast, but nothing to worry about.
Focus: fast and precise. The adjustable limiter is very useful. Focuses well even with the 2X TC (1st version), though it micro-hunts if the subject has low contrast.
- Hood doesn't lock when retracted - but normally that's when i'm using the front cover, so not important. Largely compensated by the fact that the hood is built in!
- Focus ring cover could lock better. Not important.
- Paint comes off real easy. I can scratch my copy with a fingernail. As some have said it's not so, there must be sample variations. This is a purely cosmetic issue.
This lens is so sharp it can be used even wide open with the Minolta APO TC 2X - but then it shows CA in contrasty scenes. Still better than the 500 F8 (unless for CA, of course, since the 500 has none).
This is by far the best lens i ever used. If you can get one, don't think twice!