I bought this for the daily commute to uni(mature student). I cycle about 10 miles a day and thought that the bright colors and hi-vis strips would be a sensible choice for the dark winter months.
At first I ordered the 30ltr variant but changed my mind because I thought it might be too big for daily use(oh, and amazon dropped the price by 10gbp after I had ordered it!) Either way, the 20ltr is a very smart, compact bag. I'm 6ft + and it doesn't look ridiculously small on my back, and the shoulder straps are VERY comfortable.
Having chosen to go smaller, I read the reviews on this site and was still a little apprehensive that my 15.6" laptop might not fit with books etc. But for the record, I purchased a targus zamba sleeve threw my laptop in and everything fits fine.
I just cannot recommend this bag enough, it's build quality is fantastic. Good seams, well padded back and straps. It has left me wanting to replace some of my old Mountain Equipment gear I use sailing with Overboard branded rig.
Lastly, overboard do seem very reasonably priced when compared to other brands of outdoors kit. The quality certainly appears to be there. But I have seen several price changes on this site in the last couple of days and it's frustrating for consumers! I bought my 20ltr for 30gbp and at that time the 30ltr had just gone down to 34gbp. At this price, I feel I got a bargain - and I'll be looking out for OB gear in future.