I was disappointed to find that the first example of a filtered index was over half way down the article, that put the whole top half not quite out of context, but sort of out of focus. Also an explanation of the lexical v logical limitation might have been useful before getting us interested in a feature that is basically crippled beyond virtually all usefulness by that one limitation (i.e. only if you're going to use the exact query in the filtered index will it actually work, IRL that probably eliminates 90%+ of potential uses). That limitation does put the whole article out of context, because every reader for whom a logical comparison would have made it useful (Over 10x as many as for whom it is actually useful) is mentally extrapolating impossible uses for it and then you slam them down to earth with an annoying thump at the end.