Put me in the ambivalent camp. They are acceptable in terms of quality and reliability, but not remarkable. What you get in comparison to other entries at the same price point is the Colt name and history, and not a whole lot of features. Contrary to other opinion, I find case support and feeding to be worse on the new production Deltas when compared to the older models, but some of that may reflect the variability in what comes off the Colt line.
I sent one of mine out to Nighthawk to be completely gutted and rebuilt, and I love it. But I like my Kimber Eclipse better than the stock Deltas.
This is the blended ramped barrel on my custom Delta:
This is my stock Delta Rail:
This is the case support on my stock Delta non-rail next to the stock Kimber barrel:
They work fine with new production ammo, and carry the Colt legacy, and I think that makes them an acceptable choice for the price point. But you get a lot more at just a short price jump up to Dan Wesson.