I've got a press caul and all the inserts for it to turn a drill press into a fret press. It's not a bad way to go if you've got a constant radius neck. But, with a compound radius, you end up having to change the insert 4 or 5 times during the course of a neck, then there's too much change from one radius to the next so you end up having to get out the dreaded fretting hammer anyway. Then, if you've glued them in, the hammer may not help as much as you'd like because the glue has set (or started to), so you end up doing a lot more levelling/crowning than you'd expect for a fresh set of frets. Any time saved using the press gets wasted truing everything up.
Even if you do have a constant radius neck, you have to start the frets with the hammer anyway. I suppose if you were a production shop or doing a LOT of fretting/refretting, the press is the way to go. But, for someone who does it once a month or so, the hammer is the way to go. You've already got it in your hand - lay a line of glue in the slot, finish the job for that fret and move on to the next one.
But, that may just be me.
I'd like to see how Warmoth does it, since the vast majority of their necks have compound radii.