I just got one of these after reading loads of great reviews and I can confirm it is brilliant if you are looking for a big-ish rucksack for cycling. It comes with a helmet holder (snigger) and a fold-away rain cover. Very, very well made and comfy to wear, I'm chuffed to bits with mine.
I've been looking out for a cheap one for a while and stumbled upon this one in the sale at Trekkit for £40, but there is a £5 delivery charge. However, I got Evans to price match, and they offer free delivery, so £40 delivered (the usual Evans price is £64.99).
This isn't exactly for everyone, but hope it helps some people out. I've had a similarly sized Camelbak before and this is in a different league in terms of build quality.