You're going to get plenty of comments both pro and con, or you can do a search for slides. Most posts are about folks with problems. Nobody goes on one of these forums simply to say their slides/levelers/anything worked well today.
As for me and the way we use our MH, slides are not required or desired. There is already too many items that need "tweaking", caulking, oiling, or otherwise maintaining to add slides to the equation. Having said that, due to the total lack of new units that are "slideless" our next unit may have some of them.
Having read many of the posts on slides, it appears to me that the smaller the slide the less issues. So a slide with just say a dinette or bed works more consistently than a full wall slide. But there are always exceptions.
My 2 cents.