the powerpoint from the Aerospace Corp is interesting, at least in regard to the examples that they present. I've seen a number of them before. The ones showing whiskers growing from the leads of SOIC packages (or smaller?) and SMD components are the ones that get my attention the most, as these are what are in the designs that I deal with. The examples of the whiskers on wire wrap posts or the card rack guides (on the shuttle!) are of less interest as they were already very old technologies when the presentation was created.
For the sake of reliability, I had the impression that military and space applications were still using processes with lead. The problem is getting packages with lead based finishes. My experience in doing work for satellites is that the customer was very conservative and was happy using parts that were long out of production as long as the design was proven. We kept some packages of the dice for an ancient op-amp that we had packaged into a can package by Lockheed everytime we sold a system. Compared to that sort of trouble, getting lead based finishes on the pins of a production IC should be easy.
There is room for debate as to whether going lead-free is worth the benefits, but I still haven't seen signs that electronics reliability has been impacted. My employer has bigger sources of trouble... one example is resistors contaminated by sulfur! There is always the possibility that whiskers could be the cause of some no-fault-found returned parts... but there are lots of potential causes. FWIW, conformal coatings and potting are pretty standard in our products, which are a slight step above automotive grade. I suspect that the low-cost commercial products are less likely to use coatings and therefore will be more affected by whiskers.
