I found the adidas footscan quite useful (the guy serving me was more helpful than the ones helping DS by the sound of it)
He brought out three suitable shoes and let me try them, mixing and matching the different shoes without a sense of hurrying me along.
The scan itself was detailed and he did explain it all.
It was free so you could give it a go and if you feel like you're not getting a good service then just politely decline the shoes they recommend?
(for the record, I haven't done video gait analysis so can't compare directly to that)