For me, finding the "perfect" case for the PMA400 is a bit of a lost cause. I've tried a few now, and I can't seem to find exactly what I'm looking for. I have however, acquired a pretty good list of what I don't want. And with that sentiment, I offer you the following review of the Covertec Luxury Leather Case for the PMA400 (and AV400).
First Impressions
They say to be sure to make a good first impression, because you may not be given the opportunity to make a second. Covertec certainly went out of their way to make a good first, for sure. The case was promptly delivered by FedEx in about 3 days. It's packaging was also welcomed with an attractive glossy cardboard outer shell with a blister pack underneath, protecting the goods.

The Opening Act
Upon opening the outer packaging (violently, with alternating sharp and blunt objects, I might add) I was pleased, and admittedly somewhat confused, to find another box inside. This candybox is again very attractive, but I'm not sure why I need it. I guess it's free, so who's complaining. So I suppose I can expect to have a PMA, in a case, in a box, in a box. Moving on...

The Case of the Case
So now we're into it. Upon handling the Covertec case for the first time, I was quite pleased. It's soft, flexible and does feel a bit luxurious, living up to its moniker. The magnetic closure works well and the attention to detail, like the outer stitching and clasp, was quite pleasing to the eye.

The inside was no afterthought either, with a soft material to protect the screen and a beveled area, presumably to prevent accidental button presses. I liked the beige interior as well, as it seemed to take hints from established automotive design (different interior and exterior colors).

I'm fairly certain that that's about the time the excitement wore off.
Covertec Fits
The PMA is secured in the case via two fitted plastic clips, top and bottom, that prevent the device from sliding around and out of the case. While I do offer kudos to Covertec for providing a secure, tailored fit, once in the case, I had began to have my doubts. Against the weight of the PMA, the case now seemed flimsy and not likely to hold up to the rigors of daily travel. I'm confident, it won't fall out, but if dropped or banged around, I'm not sure how much protection it will offer.

But it looks nice.
I also found that simply holding the case on the right-hand side, much to my chagrin, caused accidental button presses. So much for presumption, let alone beveled innards.
But it looks nice.
Not a Leg to Stand On
I was hoping -- really, really hoping -- that this case offered a stand-up option, much like the Archos case (it looks very similar in structure). Unfortunately, I only had hope because Covertec was unable, or unwilling, to answer this simple question over email and offered no phone number to contact them directly.
Well, I found my answer, and that answer cost me $35.00 USD. It does not.
And the worst part is that it could. Covertec chose to stitch the other side of the closure into the case. This certainly will prevent strap-loss, but does nothing to help the case stand up all on it's lonesome. Sad, really.
The other bothersome item is that this was clearly designed for the AV series as there is nary a stylus receptacle to be found. There is no way whatsoever to store any stylus with this case. While clearly adding some convenient resell for Covertec, it does not serve the PMA400 to the fullest.

The Final Wrap Up
I wanted to like this case, but it did not make it into the inner circle of pointlisse. While this review was largely negative (positive reviews are just so boring, after all), there are a few things worth mentioning, and most of them are aesthetic in nature.
I would happily recommend this case if you:
I am none of these. I don't mind a good looking case, but prefer a good working case. If you're still interested, Covertec still has them in stock, but you may find one on eBay soon. Just a hunch.
Oh, and for that last point, above... I guess we figured out what the candybox was for -- protecting the case. But who will protect the box????
Covertec Multimedia Luxury Leather Case:
http://www.covertecstore.com/en/t-mp3/rm-AV400/mp3-archos-av-400.html