I tried one of these for the first time last night. I loaded one in to my DE89 and was rewarded with one of the smoothest shaves I've had in a while. Not just smooth but close too and it dealt rather well with the tough stubble on my chin that even a Feather has a hard time dealing with. They're dirt cheap too so all in all a very pleasant surprise.
If you're in the UK you can get 100 for £7.90 delivered, same vendor does a 10 pack for £2.75 delivered
http://www.ebay.co.uk/itm/100-Croma-Diamant-Double-Edge-Safety-Razor-Blades-/300971080218