It all really depends what you are looking for in a delay pedal. For me, I'm looking for a good variety of potential sounds, different memory slots so I can use different delays during songs, tap tempo, and reliability.
The DD-20 has all of these features, at the best price. Of it's direct competitors, the Nova delay has a number of reported noise issues. The Timefactor is exellent, but much more expensive.
Another little known point about the DD-20 is that it does no AD-DA conversion to your dry signal at any point, whether on or off. The only digitally produced sound is the actual delays. I would never in a million years be able to tell that the "analogue" and "tape" modes were digital if I heard them on a recording anyway.
Can you tell I like DD-20's !!