First of all this is a karambit. A karambit without the retention ring, but it is still a karambit. Don't try to adapt a straight blade style to this, learn to use a karambit.
The lack of the retention ring does cut off some options- you can't do any of the flicking more traditional styles seem to favor, but frankly I've always thought that stuff would just get me a broken finger anyways. The lack of the ring puts you in either a hammer or ice pick grip and makes switching from one to the other more fluid and simple than with a retention ring in the mix. Using the butt end for blunt impact is not as easy as if it had a ring, but you can still do it, assuming you have smallish hands.
The blade does not come overly sharp- at least not mine-, but that's not such a big deal. You can of course hone it if you wish, a little tricky with the swept forward design, but really because of the shape of the blade you will find that cutting, or rather tearing through your every day jobs will be much easier than you would think.
I don't know what some other reviewers are talking about, karambits and hawkbill blades are EXCELLENT utility knives. You simply poke the point into whatever stands before you and pull the blade through, and because of the inward curve, your cutting surface stay on the blade and is drawn across it rather than mashed against the way you might find yourself doing with a straight blade. The shape also makes it easier to get a cut without much dexterity in the wrist, streamlining motion and speeding things up, even if just a bit.
Not a knife for everyone, but if you hate clam shell plastic packaging and have any interest in a knife fighting style that relies more on cutting and manipulation over simple stabbing then this is definitively worth looking into.