For items that have been around since gen. I, those items never really stood out to me. In a game where every turn counts, I don't find raising one stat by one stage to be very useful (unless you are in the early stages of the game, where said items aren't very plentiful from what I recall). I just find that turn better spent on using a move or healing my Pokemon, not raising a stat with an X-item. Plus, as others have mentioned, boosting moves like Swords Dance and Dragon Dance exist, which do the same thing but yield more favorable results. Yeah, the X-items could potentially have their use, but I just forget that they even exist in the first place. So, short answer; no, I don't use them.