Lately for (solo) overnighters i've been using the Sea to Summit Ultra Sil Day pack, which is only 20L. But, i also don't bring stove/cookset on these trips, there is usually plentiful water where i usually hike, and i don't have the appetite of the typical over fed, Westernized grizzly bear. (if hiking with my wife, i bring a bigger pack and let her carry the Sea to Summit one).
But this little pack allows me to pack all the essentials for my trips, EE 40 degree quilt, Stoic Hadron jacket (don't always bring), S.t.S NANO bug net (don't always bring), poncho tarp w/ cord and some stakes (don't always bring), NeoAir all season medium pad, Sawyer squeeze filter & bag, kite tyvek bivy (don't always bring and if i don't, i bring polycryo for groundsheet), headlamp, and pair of warm sleeping socks. I'm actually surprised how much i can fit in there.
If you pack really light weight, you don't need any bells and whistles of hip belt, etc. Some people may need a sternum strap with this pack, but i sewed some linen-poly material onto part of the slippery shoulder straps and don't need a sternum strap. I also like that it's innately highly water resistant--minus the zipper area and seems.
Anyways, not ideal for most people, and i doubt the durability is all that great, especially not for people that do a lot of bushwacking, but it works for me so far. Oh, and it weighs less than 3 oz stock (the linen-poly on the straps adds a little extra).