Hexamine (such as ESBIT brand) stoves are very interesting.
Ultralight hikers prize them for their light weight, but they can be a nice addition to any kit as an emergency stove. They've got about the most stable fuel around. The fuel doesn't evaporate or go bad. You can generally burn 40 year old fuel that hasn't been sealed without problems. I keep mine sealed and protected (they can be crushed or chipped pretty easily), but I've seen some old hexamine fuel that burned just fine. They're great for long term storage in a kit that you don't plan to touch often.
The down side is that they don't put out a lot of heat, can be hard to light (particularly in wind), and the low velocity flame really needs a windscreen. They also leave a residue on the bottom of your pot. I usually keep my pot in a plastic bag if I'm going to be burning hexamine.
One trick for lighting them is to set the tablet on the edge of the stove at first. Get your flame under the tablet. Once it's lit, then move it to the center of the stove with a stick or something. This trick is a little easier with the larger ESBIT brand rectangular tablets than the smaller "pill shaped" tablets that some companies produce.
Hexamine's not bad stuff, but it's not particularly powerful either. It's worth playing with it a few times in order to get used to its quirks. Don't set it down in the bottom of your pack untried and then expect to pull it out and be comfortable with it out on the trail. It's no big deal, but it's worth getting used to how to light, how to cook with, how to extinguish, etc. before you head out.
Despite the fact that hexamine is not volatile, hexamine is not permitted on airline flights. Hexamine is a precursor to explosives such as RDX/Cyclonite. You wouldn't want to go into an airport with the scent of hexamine about you.