My road shoes, which I rarely wear, are a 10 mm drop. BUT! I also run in trail shoes with 10 mm drop (NB 101), 4 mm drop (Saucony Peregrine), and 3 mm drop (Inov8 X Talon 190). I pretty much love them all (well, I don't LOVE the road shoes but they are fine...for a road shoe) and like to switch it up. And, honestly, I can't really tell the difference between the NB 101 and Saucony Peregrine (other than the Peregrine has more cushioning, which makes it better for very long distances. The NB shoes make me feel really fast, though, because they are so low to the ground and light. Anyway, I digress.) I have some other trail shoes that are probably about 10 mm drop but I dislike them for other reasons (cuff is too high). I also ran in a 6 mm drop Inov8 for a couple of years until they changed the last (so it no longer fits properly--grumble).

FWIW, I am naturally a forefoot runner so my calves are always tight. That's the place where you'll probably notice the change the most as the shoe gets shallower (unless you are like me and have perpetually tight calves). Shallower shoes don't work for everyone. It's not a crime if they don't work for you.