What's so special about Mick's Special Stash?

Twas morning in Freeside and at Ralph and Mick's
Not a creature was stirring, except for two chicks
on a mission from Elvis, to investigate
a bodyguard who seemed suspiciously great.

When what to our wondering eyes should appear,
but a couple of thugs, wearing blastmaster gear!
Though we killed them, the battle was needlessly tough,
And we realized we needed lethaler stuff.

So we entered the store and a Speech check we passed
and Mick's special weaponry was ours at last.
But then when I asked for the regular kind
the stuff was the same! No stairway! Denied!

"What gives!?" I exclaimed as I looked through the FAQ
"Does Mick's special stuff replace the regular rack?
Or is there some difference that I didn't note?
I'll ask on Arqade! They can help me, I hope!"

Easy speech check,
Charmed, Mick presents wicked unmentionables,
Courier not impressed.

After you pass the speech check you cannot get the normal stuff. From then on, his shop is always contains the 'special stash' items. Even if you do not ask for them. At least as far as I recall.

The most special item Mick has in his special stash is the Naughty Nightwear. One of the few items that raises luck, and the only one that is easy to get. The other requires access to the legion high fame bunker.

You also get a few better and rarer weapons. Iirc Mick is one of the few vendors that can sell the Mantis Gauntlet. The exact mechanics are not known as far as I know. I do know that after the speech check, Mick is a lot better shop than a normal random travelling merchant.

The game also rewards you with a nice animation, a cool quote, and a few easter eggs from fallout 3. (Look at the secret stash wall). And it is great backstory. The nice mom and pop store with the annoying town crier is actually an illegal weapons dealer and forger. What more do you want? Answers in rhyme? A haiku with every purchase?

If you have the gun runners dlc, the special stash also contains the Nuka Breaker which is a reference to an awesome youtube series.

So that is what is so special about Mick's special stash.

According to the wikia ( i.e. ymmv ), it compliments his current items. Perhaps waiting for the stock to refresh will introduce new items? If not, sounds like a bug to me.