Besides Delta, have you also tried buying ITA generated itineraries
from general travel agents like orbitz?

No. I have used ITA for some time, mainly for pricing. This was the first
time that I actually booked from one of their itineraries. What has
usually happened...I go to ITA, check on pricing, routing, airline, etc and
then go either to the airline website or orbitz, travelocity, etc to
actually book my flight. This was the first time that there was a
"conflict" in that the routing that showed on ITA did not also show on
Delta.com.

I should add that, because I was using "bump" coupons, I had to use
Delta.com as you cannot use them thru a TA (or so I understand).