I do not have a slide but I have looked at quite a few with them. I see little advantage. Typically the dinette area slides out but often the dinette is no bigger than in a camper without a slide. The big difference in space seems to be the extra floor/aisle space. Personally that means very little to me. Of course there is also the newest big sized campers with multiple slides. Those often require at least dualies and often 450 or 550 level trucks and are not feasible for many of us.
If you do get a camper with a slide, I recommend you make sure the camper is totally useable with the slide in. I often stop during the day to cook a meal, use the restroom and maybe take a nap. I don't want to have to deal with a slide. In many areas, such as truck stops and rest stops, using a slide would not work even if I had the patience to deal with one.
Another issue is stealth camping. Some people seem to believe this is some sort of nasty, illegal behavior. In fact sleeping in your camper overnight is legal in most areas of the country. Many decades ago most of the vagancy laws were found to be illegal by a Supreme Court decision. Even so local LEOs have a lot of leeway. You don't want to be obvious, make a nuisance of yourself or try to extend a slide.