The Ayoob is a great EDC.
It works well for utility tasks. The blade is thin, with a nice belly.
It goes through cardboard, letters, plastic, and rope like butter. It even works well in the kitchen, though it's not the best for chopping.
The VG10 steel holds an edge well.
It is a very light, thin knife, and is easy to carry. Folded, it is deceptively small.
The handle is well shaped, and can extend the length of the knife, depending on grip. It's also easy to do the spydie-drop on. The lock is strong, for a lockback. It takes a little while to get used to the blade angle, but once you do, you'll wonder why more knives aren't that way.
Overall, it's just a great knife.
I'm not qualified to comment on it's defensive uses. I would guess it would be pretty effective. I believe Massad Ayoob is pretty well respected in his field. I doubt it would be as effective as a .45 caliber round, but, honestly, I don't want to find out either way. I use it as a utility knife only.
For a great EDC, get the Ayoob. You won't be sorry.
-- Rob