I used a Mountainsmith Phantom in 2005-2006. It weighed around 2.5 pounds (IIRC). I never really liked it that much; it rode on the top of my butt in an uncomfortable but not painful way. I sold it when I bought a more comfortable but heavier Golite Quest in 2007. I’ve been through several other packs since then.

When I was looking for a pack for my upcoming northbound JMT hike I looked again at Mountainsmith but didn’t find anything I liked; too heavy and too many straps, loops and other bells and whistles. I finally settled on the new, 36 oz, Elemental Horizons Kalais. I’ve used the older, somewhat smaller, Kalais for about 6 years and like it a lot. The new model is a bit bigger, a bit heavier and even better IMHO.