I tried a 20L Osprey cycling pack, liked it, but it had too many 'cycling features' that I don't use that cluttered up the 20L available. So now I am using a 30L osprey cycling pack and it is nearly ideal.

Actually in between I tried a 30L Osprey non-cycling pack and I could not ride with it at all (internal frame for daypack jammed into my neck...) but I really loved that pack for hiking and travel. So now I have the 30L cycling pack for commuting and a 40L version of the original non-cycling pack for non cycling.