Gait analysis is not the be all and end all, it isn't foolproof and it doesn't provide all the answers. I do feel however, that it is a useful guide and will give a reasonable indication of what the feet are naturally trying to do. I will always ask the customer if they have run much on treadmills before, because if they haven't then the results will be less reliable.
I will sell them the shoe that suits their running style, whether that is neutral, over-pronating, under-pronating, forefoot running, pose, chi or whatever. A shoe will only change things to a certain extent, if there is still a fundamental issue with regards to someones biomechanics then I will refer them to a physio. I take great pride in the fact that numerous physios in my area recommend people to me for their footwear.
Ratzer - If people want to correct their gait, I will help them as best I can, but the majority simply want a shoe that will help them run injury free. The best analogy I can give is that a sprinter will spend large amounts of time refining their technique to make it as efficient as possible, because fractions of a second can make a difference between winning and finishing nowhere. Distance runners in general tend not to have the time/inclination to do the same so simply put their feet in a different pair of shoes and hope that will sort the issue.
Bos1 - If you want to buy 4 pairs of shoes in one go, please come and visit my shop!!!