-less likely to be stolen (maybe)
-ugly ass bike (subjective, of course)
-time and money spent
its not like the bike will be instantly theif-proof. the wheels, gears, and chain will at least still be recognizeable as in tip top shape. it might stop a bike thief from considering stealing it if he was like 20 yards away, but if he gets close he'll see its just a really good bike with a paint job. a crappy bike doesn't look completely rusted out. in fact, most crappy bikes only have a few paint flaws, and rusted out drive trains. you will still have to lock it just like you would a nicer bike, so its up to you to judge how much of a deterrant it will really be. in my area, i don't see bike theft as being a very large concern, so i would never consider doing this to my bike. i would only do it if bikes are stolen left and right around you and you truely think it will stop someone from doing it.