I live up in New England and between the hot humid summers and the bone dry winters I'm adjusting the truss rod way more often than I'd like to... the side mechanism is a real blessing for me. No messing around with cover plates + easy access. No complaints here. Except that I wish I didn't have to use it quite so often.
I only have it on one neck, in theory it's fine by me - but Warmoth necks don't wiggle around anyway. I kind of wish you could get a modern neck without one, or at the very least Warmoth should supply a maple dowel of the right size to plug the little black hole, cause it sure is ugly.
P.S. (Why does the spellchecker on the Warmoth site flag the word "Warmoth"?)