I actually read your write-up before starting the process--thanks for putting it together!
Yes, I used Apple's D-U-N-S lookup form. Here's a quick summary of what's happened so far:
The first time I submitted the request for a D-U-N-S number through Apple's form, I did not receive a call. After ten days, I called D&B to see what was going on, and they said they didn't have a record of the request. So somewhere between Apple and D-U-N-S, the request was lost.
I submitted the request again, and I got a call from D&B five days later. They sent the D-U-N-S number after the call, but their email indicated it wouldn't be usable for 14 days! I tried it on the Developer Center registration form anyway, but, like they said, it didn't work, so I waited.
At the end of the two weeks, the Developer Center was down for new enrollment--for another two weeks. Once it was functioning again, I submitted the enrollment request with the D-U-N-S number.
Twenty days later, I received an email from Apple telling me that my LLC's legal status wasn't listed on D&B's profile, so I'd need to work it out with them. Oh, and I'd need to restart the enrollment process.
After contacting D&B, I received conflicting emails from them, one telling me that "my request was complete" and one sent at exactly the same time telling me that the changes would be made within the next week and a half. I sent Apple an email detailing this and asking for the enrollment to be continued where it left off rather than going to the back of the queue--which was twenty days the last time--so we'll see if that goes anywhere. I've read some accounts of having a months-long ordeal ahead even from this point in the process.
I realize things are probably a bit worse at the moment because of the Developer Center problems, but that doesn't change the fact that this process is extremely off-putting and it sours me a bit to development on their platform.