NEC/Mitsubishi's aperture grille screens (The SuperBright NEC's and the Diamondtron Mitsubishis) are the best CRT's. Their LCD's and regular CRT's aren't terribly special, but the aperture grille CRT's are great.
So a 19" Diamondtron NF for $140 is a pretty good deal. If it actually says Diamondtron NF, though, it's an old model. The current model Mitsubishis say "SuperBright Diamondtron" in the top left corner and "Diamond Pro" in the top right corner. Diamondtron NearFlat was the older ones. Diamondtron TotallyFlat are the new ones. That said, it's still probably a really good deal. I would just make sure you can take it back if it has any trouble, since it's not new.
If you're getting a new CRT, generally the NEC versions are a few bucks cheaper (and they're the exact same thing as the Mitsubishi ones).