I got an XL for emergencies, but I pull it out occasionally in summer because it's fun to use. As promised, fuel can be twigs, dried bark, pine cones and just about anything else you can get to burn in a campfire. I've burned dried corn cobs and sawdust without problems. Once it's burning well, there's plenty of heat, making it almost as hot as a propane stove. But it doesn't tolerate wet wood very well, and if you manage to choke out the fire you'll get impressive amounts of smoke instead of heat. Keep substances that burn with low heat (wax, plastic) out of it.
When you set the output to high (the fan has two speeds), you generally need to feed in more twigs as you cook, but the overall efficiency is little short of amazing. A few handfuls of twigs of thumb-thickness will cook a simple meal. All that's left at the end is fine ash, and not a lot of that.
Why not 5 stars? First, it's a little fussier than a propane stove - you need to keep an eye on it and occasionally move the food to feed in a few more twigs, and the heat output tends to vary based on how much wood is left and what stage of burning it's at. Second, it needs batteries to run. You can buy a little solar charger from the company that sells it, to keep the batteries going, but it's a small and low quality charger, and even going all day in bright sun, I question whether it would really keep the batteries full, if the stove was used 3 times a day, every day. Third, getting it fired up takes practice - or a teaspoon sized splash of lamp (paraffin) oil on top of the twigs, which works without fail, but brings you back to dealing with bottled flammables (since I use this outside my house, that's not a problem for me, but might irritate a backpacker). Finally, while I've yet to tip it over, I wish it had a wider base.
But it's much less fussy than cooking over a campfire, far more efficient, cleaner, and there's no fuel cost other than the occasional battery. No propane canisters to store or dispose of. It stows well and is simple and sturdy.
Addendum: Eventually I developed a problem with the solar power supply (the jack had a loose wire inside). I ended up replacing the cheap thing with a rechargeable 6v battery I had left over from another project, and a dozen or so 100ohm resistors in parallel. This solution has worked wonderfully, and I've cooked dozens of meals on it. I love the fact that my property produces more free fuel (in the form of sticks and downed branches, and sunlight to recharge the battery) than I ever use. This is a great stove to own for outside cooking, and for emergency backup when the power fails.
As an added bonus, when the cooking is done and I put a pot of water on to clean with, most of the trash - napkins, most food packaging, even eggshells - can go into straight the stove, where they rapidly turn to ash. It makes for a neat and clean cooking solution.
Addendum: I put this thing in a backpack (the XL takes up half of a small backpack, but there's space inside the unit for batteries, hot mat, lighter, spork and other necessities) and hiked down to Tannery falls in the Berkshires. All we had was wet wood (it had rained the right before), and starting the stove took a little patience, some birch bark and a little olive oil. But once going it burned well, and the small stock of not-completely-soaked sticks we gathered boiled water, cooked a simple meal and then boiled water again for cleaning up. The total waste was a quarter cup of fine ash.
Now, as a backpacking stove, it's hard to know what to say about the XL. A single burner propane stove can be as light as 2 ounces; this weighs much more. A propane stove can give you heat in under a minute. In wet weather, you might spend fifteen fussing with this woodgas stove, unless you cheat with some white gas. The heat from a propane stove is easy to adjust. The XL has two speeds (three if you count removing the power), and the kind and condition of the wood affect the heat output. And the propane stove doesn't need a battery, and a small canister of propane will last you a few meals easily. The only thing the XL (and better, the LE) really has going for it is if you're going to backpack for a month, dragging canisters of propane with you is more weight and annoyance than you would like (and you can't leave them behind, like you can a handful of wood ash). But I don't do that kind of backpacking.
But it's the XL I grab for short trips into the Berkshires, or cooking in my backyard. It might be that the kind of cooking I do is Guy Cooking, and I don't need fine control of the heat. Stew, soup, coffee, meat, pancakes (set the stove to Low!) and eggs is pretty much all I ask of it. Maybe I like scrounging for my own fuel. Maybe it's knowing that it can't leak propane at me. Maybe I like fussing for a few minutes to get the fire going (though in dry conditions there's very little fussing). And maybe I like knowing that if I got lost in the Berkshires for a month, and I could only wish to be that lucky, I'd be surrounded by free fuel anywhere I walked. But this is what I like to use.