I've used it extensively...its the only steel that Ive cut a finger off with...did a mighty fine job too might I add...don't worry, I recovered...lock backs are not designed for stabbing. Remember that.
Its about like AUS-8, maybe a bit harder. Its easier to sharpen than VG10 or S30V and it has about 80% of the edge retention qualities.
I personally like it. Anymore here are my only viable picks for knife steels and my impressions of them (Im no metallurgist):
AUS-8, easy to sharpen, will take a really sharp edge, but will need maintenance, nice choice for a well used EDC like any of the Sog Arc-locks
154CM - Nice hard steel, capable of a hair popping edge on a thin blade. Medium sharpening difficult, but it holds the edge well.
VG-10 - In my opinion, VG-10 is still near the top of the heap, but I have more edge chipping with VG-10 than any other steel. Its hard, its sharp, but its relatively brittle in my use. Still love it.
8Cr14MoV - For the knives that come with it, you get a nice blade for the cost. Its a vast improvement over most American carbon steel knives of the same price range. Excellent using knife, refining the edge after use is rather simple.
S30V - Hard as nails to sharpen, hard as nails to dull. I love this stuff, but sharpening it requires the patience of a zen master. If you have trouble sharpening knives, stay away. If you can make a butter knife slice molecules, go buy 5.
D2 - Bar none the hardest steel to sharpen I've found, if you want a steel thats just a hair wimpier than Wolverines skeleton, get a big chopper made with D2. Assuming you can get an edge on it, you'll love it. Same story as S30V - not for the sharpening challenged.
A-2 - The sleeper of the bunch, this stuff is amazing. This stuff takes a wicked convex and holy geezus will it cut.