Set-neck design is very common, partly because it is the cheapest method of construction. This may be also be partially due to the fact that set-neck construction sounds a bit thicker than bolt-on construction guitars. Set-neck guitars sound great for heavy distortion rock, although the individual note articulation tends to be muddier than a bolt-on or bolt-in. Examples of set-neck guitars are Gibson and PRS guitars. In this construction method the neck is glued into the body pocket, resulting in a rock-solid neck joint with no wiggle room.
Having worked with Ed Roman for many years, I am very familiar with his "bolt-in- guitars are better" argument. Ed's pride and joy was his Quicksilver line of guitars. He modeled these guitars on the pre 1995 Paul Reed Smith guitars. Those fabled pre-1995 PRS guitars were bolt-in construction and so were Ed Roman's Quicksilver guitars.
This debated has raged for years, and since it is a highly subjective call, it will not be decided today or tomorrow. Ed truly believed what he preached about bolt-in guitars, and until I began building my own designs I felt the same way too. Now, after completing my set-neck single-cut archtop '65 Cuda guitar, I feel that we all need to have at least one of each! It's just a matter of personal preference.