M-2 will take a fine edge like 1095 but hold it longer. That is the whole point of tool steel, or high-speed steel in the case of M-2, to add alloys to make the steel more shock resistant and more wear resistant.
We discussed ATS-34 vs. M-2 to exhaustion a couple of years ago when Benchmade first came out with the M-2 AFCKs. I guess posts that old would be pretty hard to dredge up out of the archives at www.benchmade.com, or rec.knives, but it might be worth a try.
The key differences between M-2 and ATS-34 are that M-2 has Tungsten, more Vanadium, and less Chromium. The Vanadium and Tungsten form very hard carbides, thus the higher wear resistance. The lower amount of Chromium means M-2 is not stainless, and it tends to have a nice fine grain structure, meaning it takes a nice fine edge.
M-2 is capable of hardening into the 63-65 RcH range which results in very high wear resistance, but also has given the steel somewhat of a reputation in the cutlery community of being brittle. If you draw it back to around 60-61, though, it is darn tough, and still holds an edge better than stainless steels and probably still better than simple steels like 1095. M-2 is not stainless, but does contain some Chromium which makes it somewhat less prone to rust than simple steels.
In the particular case of Benchmade, the M-2 blades take a finer edge, are much tougher, and hold an edge at least as well as the ATS-34 blades.
Go into the 'office,' and click on 'Heat Treating and Fabrication of Tool Steels.' This is a truly fine discourse, very readable, about how steels are made, and how they differ. Then go to 'Tool Steels,' and click on 'Selecting High Performance Tool Steels.' This really is great, and goes into the differences between the various tool steels. While you are at this site, you can look up the specs of nearly any steel, tool or non, that you like.