Just a heads up on this IKEA backpack - I reckon this is a great commuter option.
Still available in store in the UK but looks like it's end of line - there's a black version that's potentially less optimal (looks less waterproof) but still a current product
Why is it good?
Hidden shoe compartment - completely separate from main compartment. Once you've had a shoe compartment in a bag you'll wonder how you've ever done without one. Can't understate the usefulness, particularly where cycling shoes are concerned.
Side load laptop sleeve - will take a 15" laptop no problem
Side or top load main compartment
Front zipped pocket with key loop and organiser pockets
Roll down closure (like panniers)
Synthetic rubber and polyester
It looks like it will be waterproof - certainly the zips on the main compartment look to be, plus it's a rolltop.
Bright colours may be an advantage but equally you can go with the black.
Very comfy straps including a waist strap (which, if you're an average height bloke, will probably act more like a sternum strap on a bike)
It's also going to work as an airline carry on if you don't overpack it. Packing cubes would certainly help here.
You'll easily get a weeks worth of shirts and underwear to work in this and the rectangular base gives just enough structure to hold shirts flat and reduce creasing.
Oh and how much? £29! Sorely tempted to go and buy another.