I typically don't care for "sheet-framed" packs when considering weights over 20 pounds, but Osprey packs are some of the better off-the-shelf packs on the market. My go-to day hiking pack is an older Osprey Manta (also about 30 liters):
They have some of the better features for backpacks. For this size, I could easily make it a 1-2 night load for 2-season use. Weight is the biggest issue you need to watch out for. The Manta pack has a tubular frame, but I still wouldn't want to exceed 20-25 pounds. Sheet framed backs don't really offer suspension, just frame support. Heavier loads will be felt more on your shoulders which is the reason for caution.
My only other caution would be to try some of these smaller day-packs on in the store if you can (like REI). Torso size may make them some not fit well and they don't generally have much variance in torso size. It's really only important if you're actually going to rely on the waist belt for proper load carrying. Compression is also important as most day packs used for very mobile activities need both solid suspension and the ability to tighten a looser load down to keep it from flopping and throwing your balance off.
Although it doesn't have the wire frame as the larger Kestral packs, I'm going to pick up a Kestral 28 liter pack for my son as an ultralight weight weekend pack.
ROCK6