Ian,
The thread you refer to was to identify the most compact kit possible which I took to be regardless of other considerations (possibly incorrectly). I believe it is about the most compact lens to cover in that focal length but it would not be my personal choice but is well liked by others I know. Realising the ambiguity, I have modified my previous threat to make this clear.
Whilst it is light and cheap, it does not matter how little you use it, if you find that for the one shot where you need it sufficient rise is not available.....you might have well left it at home. I also found that simply using it was enough to dissuade me from using it bacause it was so dark. I do like the focal length and so was prepared to go for something with more coverage (and more cost). For the Harvest Capella shot I did not need any movements so had no problems and with 65mm of course one gets lots of DOF at f22! Were I building a kit again I would either save or put the money into getting the other focal lengths right for my purposes even if this meant having fewer slightly more widely spaced lenses. I instead of 65 f8, 90,135 sell all three and go for a 75 and 120 or so.
Still, when shooting straight on it was plenty sharp enough just out to the edges assuming shot at f22. mine was single coated and never flared.