I've got a few of these.
My favourite is the wild woodgas mk2 but I've also got 3 different chinese clones.
I'll admit they have a bit of a learning curve and they produce a lot of heat quickly more conducive to boiling than frying sometimes, but I wouldn't be without mine.
By far the best use is as has been suggested wooden kitty litter pellets, easy 30-40 min burn and after the initial ignition period really consistent. This is what I do car camping or sometimes on day hikes.
Although I bought myself a pair of pruning clippers to quickly/easily process twigs and sticks for it and find it very therapeutic. I'll often use it in the evenings on the patio as it's so easy and fun.
Things I've found that may help.
Use driest materials possible, if the wood used is dry it almost doesn't smoke at all.
Use a windshield, although really this is true of most small stoves.
Process the twigs you want to use, I don't use anything thicker than a pencil and keep the bits 1-2 cms long, I put the thicker stuff at the bottom and then the smaller stuff at the top. I've also filled it with carving/whittling bits and shavings (you need to put bigger stuff at the bottom).
Packing it with fuel, you don't want it packed too tight but equally you don't want it too loose. there is a happy medium that should be gone for.
Topping it with fuel, I find with twigs I can get a good 20 min burn which is enough for me usually, if I need more burn time, I often wait for it to half burn and then add a handful of fuel at a time. Again after the initial burning in (smoky and sooty) I then put my pot back on. Don't be tempted to add too big pieces even when going well, it works better with smaller pieces that gassify almost straight away.
Make sure you light it from the top it works so much better than trying to light it as a normal stove. If you have trouble lighting it, it may be packed too tight.
They do produce a lot of heat underneath and when I can I usually stand mine on a very old steel plate, but I've also put it on a small raft of wood and it's worked well.
For completeness I agree they are not going to be for everyone. If you need really long burn times or to be able to quickly change heat output or want something that is very quick to use, you might be better with something else. They are not the smallest, or most easiest packed, they are probs more suited for boiling than frying (though I often fry on mine). They are though fun, you don't have to carry fuel, I like the fact they leave very little unburnt fuel, and I find mine quite easy to use now.
Horses for courses. Hope this helps.
