The first rule of interface testing: Test the actual interface, on the actual problem, with the actual userbase. This classic article is from 1989. You wouldn'

The first rule of interface testing: Test the actual interface, on the actual problem, with the actual userbase. This classic article is from 1989. You wouldn't believe what a state-of-the-art interface looked like in 1989. My awesome shiny new Mac SE/30 -- an excellent machine -- had a 512 by 342 black and white display (and I do mean black and white, not greyscale) and a 16MHz processor, which was considered fairly powerful. My point is: We lived in a totally different universe back then. So, admire the methodology, but don't waste time debating the relevance of the results. Do some new measurements on your interface with your tasks. This is especially important now that touch interfaces have finally escaped from the lab: We are only starting to develop experience with such things, and everything is up for debate again.