The M4-2 is not an M4, and the M4's command higher prices. Look here:

for a discussion of some of the differences, and of manufacturing changes to the M4-2 over its production life. There are other places to find more info as well that you should find with a google search. You should just be aware that you shouldn't pay M4 prices for an M4-2, and that what you've heard about the M4 may not necessarily apply to the M4-2.

Actually, this page is a good read for anyone thinking about buying Leica rangefinders, as it covers the whole range and discusses the main pros and cons for each model.