I've got a '97 M2 Comp that I've been planning on selling. It is M2, Specialized's Metal Matrix frame, which is basically an aluminum frame with some fancy marketing thrown in.
It's got a toptube gusset at the headtube, but in '98 they also added a gusset underneath the down tube, probably doesn't make a great deal of difference. '97's also have a head angle about half a degree steeper than usual(71.5) which makes for quicker handling. I think they backed off from that steep angle the next year, or maybe a couple years later.
it's a great frame, stiff, and accelerates like crazy. For a number of reasons, partly physical problems, and also because the frame was just a bit too big for me, I just never did end up riding mine much, so it's mainly just been hanging in my apartment. stole the wheels from it for my Rocky Mouintain Blizzard.