Wel, had a chance to try this out today. Upside; insanely simple, dont have to search for a place to put it, if you can build a fire, you can use this. Downside; feeding the fire, and the size of the fuel. Now, neither of these are really a downside IMHO. After all, it IS a fire. But, it takes some prep time to get the fuel ready. And, boiling time is a little longer (I got it in about 15 mins from ignition) as you have to constantly pull the cup off to put more fuel in.
Another HUGE upside; no mess!! Its a self contained fireplace! When youre done, no fire scar, no ring! Just ashes, that you can either pack out or scatter! I punched a couple holes through the lid, put some baling wire through it, and packed out the ashes. This is so KISS I am kinda surprised I hadnt seen this before. I wrote a little more in my blog in my sig, if interested.