I just fretted my first neck today with the Stew-Mac arbor and caul, using my 10" Ryobi benchtop drill press.
Even with a block of wood reinforcing the drill press table, it felt pretty flimsy, and I was worried that I was putting stresses on the drill press that it wasn't built for. (I probably should have used something more substantial to reinforce the table; the force of the press was pushing the table out of square even with the wood beneath it.)
The fret job came out very nicely, but I won't be using that little drill press for the job again.
If I had a more substantial drill press, I probably wouldn't think twice about using it. For now though, I'll probably get an inexpensive arbor press.