Disclaimer: I have never worn pajama jeans and therefore cannot be taken too seriously since everything I will say is based on an assumption.
I have a real problem with pajama jeans.
For those unfamiliar with the concept, pajama jeans are sweat pants made to look like denim jeans (you can find everything you need to know about them here). They stretch and give the impression of having pockets, using stitching and brass rivets. They are supposed to make you look like you're wearing jeans but feel like you never took off your pajamas.
The problem with this is that pajama jeans don't fool anyone. I don't look at the wearer--even in the infomercials--and think, Wow! I never would have guessed those jeans aren't real. You should look like you cared when you got dressed; instead, pajama jeans say I wanted to look like I cared, but I went above and beyond to not care by putting on these sweat pants. Not only did I not feel like putting forth any effort today, I put what little effort I exerted into not caring.
Denim provides support and makes you look a little more put together; pajama jeans, not so much. They are supposed to fit any size, but the problem with stretchy fabric that has stitching is that you can see the stitching stretch. All illusion of structure is gone when the stitching of your "jeans" starts to show the contours of your less-than-toned body (I say this assuming most of the wearers would be like me and have a few lumps to show off).
If you feel the need to wear lounge clothes, my opinion is that you should either be lounging or call a spade a spade and wear real lounge clothes. Own up to the fact that you dressed lazy today, but don't insult me by thinking you fooled me. And don't insult yourself by thinking you pulled it off.