A simple-to-use,get-out-of-a-jam piece of gear. Use as your primary ignition source or as a back-up.
Pros
Simple & Reliable
I bought this back when Light My Fire used wood for the handle instead of plastic... doesn't make a difference in the performance, it just looks less industrial, like it's something from your old scout days.
If you use a canister stove, then this is all you need to light it. I don't even bother with a lighter anymore. Piezos can be hit or miss, especially in the humidity I've found. The FireSteel always does the trick with one spark... sometimes two or three on an of night.
Once you have a canister stove going, you can light anything else. I still carry some matches in my first aid kit, cause you never know.
I learned a new trick this week...you can use a tampon (unused of course!) as kindling to get a fire started! The dense cotton burns VERY well. And the video showed a guy using one of these flint strikers to get the tampon burning. Pretty awesome, especially for us women adventurers.