This is widely recognised as one of Canon's best value L lenses. Currently this price is the best it's been for almost 2 years. (it is in fact £1 cheaper from Devon Camera - but I cannot post that deal here as Hotukdeals do not recognise this shop!)
The lens itself is light (relatively speaking), well built and has a super image quality that is probably second to none at this price.
Canon users who know their stuff will already know this and will only struggle to choose between this, the IS version at £799 (Warehouse Express) and the very expensive and heavy f2.8.
The images are simply sublime from this lens. If you need to get into L lenses this the way to go!