Here at WordPress.com, we have over 200 themes (and even more plugins) running inside the biggest WordPress installation around (that we know of anyway!) With all of that code churning around our over 2,000 servers worldwide, there's one particular WordPress function that we actually try to shy away from; query_posts()
If you think you need to use it, there is most likely a better approach.
Really good explanation of why you shouldn't use query_posts; a function I know I've used in the past but definitely stay away from now :)
