User Review: MSR Heat Exchanger
Price Paid: $39
I have used this item for 10+ years. I've forgotten when I actually bought it.
It does what it says it will do. It increases efficiency and saves fuel. It does work a bit as a windshield too but I wouldn't count on it for that in a strong wind. It is what it is, it's not designed for that.
I didn't fully appreciate it till this year however. I forgot to pack it for a trip I took and it felt like it took forever to boil water without it. In my opinion it's worth its weight.