That's what I use for a daypack/bookpack as well, although it has to be about 7-8 years old now. It says it can hold 30 litres but that's only if you stuff the side water bottle pockets and the back mesh pocket. In reality it's more like a 20 litre pack. I have an honest 30 litre daypack that I can stuff a lot more in it. (I have 6 backpacks in total.)

What I do like about the pack is the small waterproof pocket on the back. This is where I store my PSK, FAK, whistle, compass, SOAP notes, etc. I strap my Leatherman /w bit kit on one of the side straps, my camera /w spare batteries goes in the one of the side mesh pockets. The hydration bag sits in the pocket nearest the back which leaves the main pocket for gear like a jacket & lunch and the smaller secondary pocket for things like keys, pen/pencils, twisties, headlamp, etc. I suppose that if I used the lashing staps on the bottom I could really load it up if I wanted to.

The really fun thing about this daypack is that the waistbelt folds and hides behind the main panel. Most of the time I tuck it away on my trips to and from the office. On occassion, I will do up the chest strap and for heavier loads I will loosen the load levellers all the way and do up the waist belt so that the weight sits on the hips. 20#s is about the max you might want to use comfortably but I have toted a 25# load occassionaly.

It's uncommonly versatile - good for day hikes as well as a book pack or computer bag for my 14" laptop. It doesn't look obtusive or too colourful (mine is grey).