Hawkbills are surprisingly versatile. Many a man has looked at them and thought, sheesh, that's so specialized it's practically useless -- and then bought one and found he can do almost anything with it. There are some things you need a belly for, like skinning, and if you only carry one knife it has to have some belly (IMHO), but if you carry two knives and one of them is a korambit you'll find yourself using that one more. The things you cut with it for could be cut with the other knife, but the korambit cuts them more easily.
Sharpening isn't really any harder if you have the tools. If you're too cheap to buy diamond you can wrap sandpaper around a dowel rod.
I'm assuming you're asking about the korambit-inspired hawkbill knives that are proliferating recently. If you're asking about real korambits the answer is different. A real korambit is double-edged so you have a nice long curved belly to work with but whichever edge you use you can't push the spine with your thumb. I'm constantly doing that when I use a small knife, so I would find a real korambit awkward for anything but self-defense. YMMV -- I've noticed some people seem to be able to live without putting their thumbs on the spine.