I agree also. I don't need a link to Quicken, but this is certainly a feature of Quicken I like. On more than one occasion I have written a second check when this feature would have alerted me that I had already paid the bill. I also agree that it would be a big time saver! Very often the information is similar.
I also would like to edit checks before they are printed rather than having to void the entire purchase and reenter it. This is another handy feature of Quicken.