I was looking for a daypack that fit well, had some structure to it, and could carry up to 7 liters if needed.  I own a few similar daypacks, but this one caught my eye.

This pack serves me well on any of my short day hikes.  I can put a full 3 liter and 2 liter bladder inside of it (either size fits in the hydration sleeve behind my back, and the other one goes in the main body), and I can also put my rain gear and snacks in the main compartment as well.  The top zippered pouch is perfect for putting your keys, wallet and phone or other small items that you need to keep handy.  The side pockets can hold a 1 liter water bottle each, adding another 2 liters of water capacity.  Even with 7 liters loaded in this pack, it's not heavy on the shoulders because there's sufficient padding on the straps.  An elastic loop on each shoulder strap allows you to run your hydration tube through it to keep it handy, or you can use this loop to attach a camera pouch or other small item that you want attached within reach.

There's no need for a hydration tube port because the bladder sleeve is outside of the main body and behind your back.  The padding on the back of the pack is comfortable and provides a bit of structure to the pack so it's not a saggy bag hanging from your shoulders.  It's a good fit for my 6'1" frame.

I removed the waist belt straps from my pack as I didn't see them necessary to stabilize the load while on my back.  The waist belt is removable so you don't have to make the decision of cutting it off or not.  Simply remove it from the buckle and store it away for later use.  I'm not a runner, but I tend to jog downhill on trails and this pack stays in place.  The sternum strap does a fine job of keeping it centered.

I'm very happy with the design of this pack.  It's compact, efficient, doesn't look dorky, and it's built quite well.  I've put over 50 miles on it already and it has replaced all of my other daypacks.