I agree that it would be nice if the search was better at guessing what I meant when I misspelled words (although that is arguably my problem, not theirs).
Also, having indexed a number of books and thus looked very closely at recipe titles, I have decided that cookbook editors allow their authors a truly remarkable the degree of variation in spelling and nomenclature! (which in turn makes it hard to guess how some words are spelled).
But one thing that the search function does really well is provide results that use the various alternate names for ingredients used in the various English-speaking countries.Look for "eggplant" and you will also get "aubergine", "courgettes" when you are looking for "zucchini" (ironic that the first two examples that jumped to mind were actually French words used in English-speaking countries, but you get the idea). It is also very educational. Look for beets, and you will get recipes for beet roots, but also (down the bottom of the list), recipes for chard (which is called silverbeet in other parts of the world). (I confess, I thought this particular search result was an error when I first encountered it!) I've learned a number of fun facts through the search results.
I love the + and - functions to limit searches by ingredient, but I'd like to have an index to the ingredient categorization. I always have a hard time figuring out categories for such things as honey that (at least to my mind) could be considered a baking ingredient, under sweeteners, or perhaps is a pantry staple, etc. (Perhaps there is already such a thing?) Still, I find that in looking for one thing, I often find something else intriguing.