I've got a JetBoil. I think it's great for boiling water. Tea, soup, boil in the bag meal. Really frugal on gas. Everything packs into the pot, incl gas. Piezo already attached. Littel cup attached on bottom, with room for tea bag, or coffee sachet.
In some ways it's better than a flask because you can choose what drink to have on the fly, and tea is a bit naff from a flask, IMHO. Boil in the bag is good too because the pot is quite tall, so you can roll up the meal and stuff it inside. The pot has a neoprene cosy which means you don't lose much heat out of the sides. They are a bit pricey, but for convenience I think they can't be beat.