I bought a six pack of lightly used ones from CTD for $9.99 with milspec trioxane fuel about 15 years ago, just to have during hurricane season.
I played with them when I first got them and actually used them during Wilma in '05, when my power was out for 15 hours. I was able to heat some things up like soup, chili, water for tea...stuff like that. The problem with these things, is that you can't use normal cookware, you need the thinner camping stuff, otherwise the typical household items acts like a huge heatsink and things heat up much more slowly. This holds true with other stoves as well, not just the Esbits.
I go to the Army Navy surplus store and buy trioxane, although I've moved on to the Trangia, Coleman duel fuel and propane stoves/BBQs. I even have one of those folding Sterno type stoves, so the Esbits are relegated to back up status, or giving to condo neighbors, in a pinch.
Chris