Well Dave, what would I do if I found something to complain in whatever lens or body and the manufacturer doesn't help? I'd go and post in a forum, or more.
What would I do if everything is fine and I get my pictures under all, even weird, circumstances? Going to a forum and write "hey, guys, everything is cool on my side"?
And how create complaining threads kids and grand-kids? "The internet is full of..." that part of the sentence I always agree with
I will not say, I always get focus there where I planned to have it sharp. I just can't say I miss more shots with Sigmas than with Nikkors. I don't do statistics on sharp or blurred pictures, I just delete the ones somebody - me - or something - lens, body, subject movement - messed up.
<Edit1>I'd found it interesting to know if the complainers have other, "better" genuine lenses to compare? Best would be the same FL and aperture. Which bodies misbehave? How experienced are the complainers? Expecting everything great out of the box?
Hmm, with FoCal I could do an AF reliability comparison between some lenses, would you like to see one? Of course. that's only one or two bodies and only lenses I still have a Nikon and a Sigma version. But the test is running automatically once it is set up. Even then, doubts would remain: I could have the one in a million exception Sigmas which works fine or the one in 10 million Nikkors which is a lemon. <_< </Edit1>
For the 18-35/1.8, the D7100 got better keeper rates than the D7000, but after a while I just didn't use the D7000 anymore, so the relations for that body/lens combi got worse because the other was used exclusively. Most pictures I can't take twice, so I really have no base to compare directly. But what I saw: Once I suspected AF problems, I always found pictures confirming them - and others telling another story. I just don't know...
<Edit2> With the 18-35 I found sometimes no subjects big enough to cover the AF point marks in the finder. I simply had no idea if the AF prefers a lamp post, a railing three meters behind or something contrasty 500 meters away? So there was sharpness on one of the three items but I was not blaming the lens because I was not certain on which phase focus was detected. Does that make sense? </Edit2>
As for the Fuji, I only did some 100 shots and getting used to a different menu, button layout and AF behaviour. I missed sharpness with one shot, which I find a good rate. Manual focus help is great with an EVF, although at times it is too dark. Bright sunlight and looking into the EVF: lots of shadows :unsure: while the LCD is okay. Have no explanation for that. While in darkness the EVF appears to be better than an OF.