I managed to have more of a proper play with it today. First things was to sand down the handle to get rid of the varnish, and it's now being replaced by a few coats of Danish Oil. Much better already. The handle is "utilitarian", but I kinda like it. It'll be a user tool anyhow, and it provides plenty of secure grip when whirling it around.
I also spent a short time on the whetstone to get rid of the wire edge. That's gone, although I can't really say I've managed to get it super sharp, but that's mainly down to my lack of sharpening skills and shortness of time today. However, the main problem is that the edge at the hook is blunt as a blunt thing - literally about half a millimetre of unground thickness there. Because of the angles it's not something that's easily doable on a whetstone (at least with my limited skills), so I'll have to attack it with a file or something.
I needed to split up some half-round logs for kindling, for which I normally use my cheapo Stanley hand axe, so I gave the billhook a go. And I loved it! It's nicely weighted in the hand, and I could either give it a good whack or more gentle nick as required. Also, as it's a thin blade compared with the axe I think it's probably better than the axe, as it's more refined - you split bits of wood off the log as opposed to the axe hurling bits of wood at all angles. There's less risk of nasty glancing blows. Also, once you're half-way through the log a quick twist of the hook and the kindling pops off easily - very nice.
I do need to keep practising, though, to get used to the different uses of the pointy hook and the flat bit - they sometimes got in the way of each other too.
I also needed to get rid of some rampant bamboo. Normally I hack at it with my pruning saw, but thought the billhook might do the trick. Unfortunately the most useful part of the blade would have been the hooked edge, but since this was still so blunt it was useless. So I gave up and went back to the saw. Once I sort out the edge properly I'll try it again.
My actual hedge is too young and small to need laying yet, but hopefully in a year or so I'll be able to use the hook for in its native habitat!
So, it's not perfect, and still needs a fair bit of work on the edges to get it in full working order. But it's great for the kindling already, and once I sort out the rest, I'm really looking forward to using it in the future!