When I think PAF replica, I'm looking to the right dimension/shape screws, correct alloys and plastics used in all construction details, correct 'L' on the baseplate feet, correct dimension TV shaped cover, accurate magnet compositions, correct slug 101 and leesona winding patterns, random under and over spec wire, a coil offest typical of PAF windings, and maybe even a Patent Applied For sticker on the base if we're really going the whole hog.
A quick browse of this website should give you an idea......
http://www.throbak.com/
But I also hang out on forums where these sort of details are the only way you can call a pickup a PAF replica, so maybe I'm more than a little biased. I also build guitars (for my own use) to as precise to 59 spec as its possible to do......so this also counts as my own extra-strict brand of bias.
If we're talking tone, I don't think you could really call any symmetrically wound pickup a PAF clone either, as the offset is one of THE critical parts IMO. Duncan seems to do well even despite this with their winds, although I've not tried many of the more recently released offerings.