I had no problem declaring my handgun at D/FW other than I had to walk about 10 gates to the little TSA office and listen to a TSA agent tell me that the cheap plastic Doskocil box I bought could probably be unlocked with a fingernail. (I had the choice of either that $20 unit or a $120 one at Academy - I should have gone with the more expensive one

Coming back from my trip to Northern Virginia was a different story. The ticket agent was nice and calm and had me open up the locked case in front of every American Airlines passenger who happened to be in line behind me so I could place the little firearm declaration form into it. I did that, locked the case, and put it back into my suitcase. All fairly calm and somewhat normal.
Then I had to walk around to the TSA area where they scan every piece of luggage. When the guy said to set the bags down and it was OK to leave, I mentioned I had a handgun in one of the bags. After watching his reaction, I had to replay what I said in my head to make sure I didn't say "I have a nuclear weapon in my suitcase". He made the wife and I stand in the corner and not touch the bag while he quickly told every other TSA agent that there was a handgun in my suitcase, you know, in case I decided to open it up and fire on everyone there.
He asked me a series of questions in rapid-fire succession that I answered just as quickly, then he wanted to know which ticket agent let me walk from the counter to the x-ray machine (about 10 yards) unescorted. I pointed at her just on the other side of the x-ray machines, and off he went to have a few words with her.
When he came back there was lots of stand here, don't touch the suitcase, no stand over there, bring the bag to this machine, are there any guns in any of your other bags?, etc.
After scanning the bag with the handgun, it all ended with "OK, you can go". I just had to ask if he was sure about that, and he answered affirmatively. I asked why all the excitement and he said the ticket agent should have gotten someone to escort me over and hand me off to TSA and she didn't do that.
My wife asked me if it was worth the hassle to fly with a handgun and after I thought hard about it I told her I would definitely not let that episode stop me from lawfully carrying where I could. Hopefully I'll never run into that TSA guy again.