My first DX was a refurb, and it was in excellent condition.
However, I was an idiot, dropped it, and got it replaced. Also a refurb, and it's been great. Scratches on the lower left corner at the bottom - can't see when reading. Looks like it hit pavement on that corner by the previous owner, but it works fine for me!
And $400 vs. $500 is a no-brainer. As to if the DX is worth it? Well, I used to have a Sony 505, and the DX screen is WAY bigger. The only reason I'd get a 5" or 6" again is for commuting or riding the trains here in Japan.