In my use of this, it hasn't been accurate. I've compared it side-by-side with another non-digital altimeter, as well as with digital and GPS, and it is off. I took it from about 11,000' to 14,000' one morning and it read about 200' to 300' short (which was not due to change in weather, since my friend's altimeter worked fine).
It is lightweight and idiot-proof, but if it's not accurate then it's no use. It's also not super-cheap (it's about $60) given its quality.
Maybe it's noteworthy that REI no longer carries this item.