Yes, arguements can be made for both sides just like any other aspect of saltwater/reefkeeping. Everyone has different experiences and outcomes. There are way too many factors involved in having a successful tank to say this one thing does it all. You can have 100 different tank all with skimmers and they will all be different in how well they do. You can also have a 100 different tanks without skimmers and they will all be different in how well they do.

I don't think skimmers are over-rated. They have long been proven useful tool for the majority of people in this hobby for many years now. I also think you don't need the biggest most expensive skimmer on the market to have a successful tank either.