I own a couple of Kuks, and have tried using all of them while out camping in the woods (i wont say while out bushcrafting, cos im not yet sure what that means
), and ive found the smaller BAS (British Army Issue) one to be the most usefull for me. If you use anything much bigger, the chopping becomes easier but the smaller tasks become harder. most kuks will have a couple of smaller tools with them, namely a Karda and Chakmak. The Karda is a small knife, and is handy, but is usually too small for any serieous work, while the Chakmak is basically a blunt knife, used for straightening out any rolls that may occur on the blade. (but is also usefull for striking against flint for sparks, and opening tins, anything that might damage the edge really). Although they work pretty well, i still carry a knife, saw, and hatchet most of the time
They can also be a pain to sharpen.
Ive owned kuks from HI, Tora, and Kukri-house, and found the kuks from Tora to be the best allrounders as far as value and quality go. (and no, im not interested in getting back into all the tora vs hi crap that went on a while ago.) Ive also owned a cold steel kuk, but found it to be a bit pants really.
I think a small kuk would be good if you were looking to carry only ONE tool, but why limit yourself. Kukris are a bit of a jack of all trades, master of none. They are passable bush tools, and very effective weapons, but if your talking about bushcraft in the Ray mears sense, then no. Id stick to the knife, hatchett, and saw combo.
Si