I've never had any problems with it either, but there are tw othings ti
does not do well. 1. Loosen rusted bolts. (I use PB Blaster for that,
it's a much better product). 2. Be used as a permanent lubricant. For
example, if the tailgate on my pickup is sticking, I will use WD 40 to
loosen that linkage, but once the linkage is loose, I apply an oil or
grease to that linkage for a permanent lube. I dont think the WD 40
totally evaporates, but there is little lube left. Thus I apply the oil
or whatever as a permanent lube for that linkage.
I have never used WD 40 for electronic switch contacts or
potentiometers. I always used contact cleaner. But I have used WD 40 on
auto connectors such as trailer light plugs, with corrosion on them. It
helps clean them, but I always clean them as best as possible too.
Overall, its top promotion seems to be to loosen rusted bolts, and I
find it near worthless for that purpose. But it does have some other
uses which are valuable. It's also works rather well to clean off
oxidation on old dull paint (on cars and other metal objects).
There are other generic replacements for WD 40 that are cheaper and work
just as well. I usually buy them.