Chapter 1. Tools You'll Need For Building Your Guitar

[Zandit75]

Not if you screw the neck on (have since seen Brendan's post about bridge positioning and clamps could apply in that instance) but if the neck holes are pre-drilled, you are better screwing the neck on.

But I don't know on what kits they are pre-drilled and what kits they aren't (and it may very well change with time). I'm sure I've seen people attaching the necks with screws for setting up their Strat and Tele kits - but that's not to say they haven't gone and drilled the holes themselves first.

My LP had a bolt on neck, and the holes were pre-drilled in the body, but not in the neck itself.
Personally, if the neck was pre-drilled, I'd still want piece of mind to clamp the neck, run the strings through, and check the holes are aligned. We've already seen issues with holes drilled in the wrong place for bridge posts and cavities routed slightly out of whack.
To drill the point home(so to speak!), I'm sure someone had to recently fill and re-drill the neck holes in the body because the neck plate didn't line up with the holes already there.