I'm the owner of an original P180. From what I know after looking into wasting some money on a P182 instead of keeping my P180, here are the differences:
P180 is silver, 182 is gun metal in color (P180B is just a black P180)
P182 has revised cable management (this is why I want to buy one, wiring the original P180 is a nightmare, especially the extension required for the ATX 12v line in most PSU's)
The P180 originally had issues with building materials in the door and the side panels. Quick changes in temperature or prolonged exposure to extremes would cause the side panels and doors to warp, leaving a concave "bowing" effect in the door. Antec replaces these defective panels upon request, and this was the major problem with the first P180's. Not a problem for most people, but mine was shipped in February of last year, so super cold temps made my side panels look like salad bowls.
Look up the 182 and the 180 on the egg and look at the pictures inside the case on the mobo tray. You will see holes in the tray for cable routing in the 182. Doesn't look like much of a deal, but if you've tried wiring a vanilla P180, you'll know what a godsend those are.
-edit-
This is excluding the obvious differences stated in product descriptions. Of course the P182 also has other differences like the water cooling holes and external fan control.