I played with Esbit for a couple of trips, too. I found that a really good windscreen, and being close to the pot was essential - I ended up using the "official" three-leg wing stove and a circular windscreen with a few holes punched in the bottom, and a diameter that left about a quarter inch opening around the pot at the top. I could boil enough water for a freeze-dried single serving meal (12 - 16 oz.) with one cube.

However, using the cubes was messy, and it left a bit of soot on the pot. I quickly went back to my canister stove; the Esbit worked, but it just wasn't worth what I perceived to be the hassle.