I don’t know that even I would say that. Not sure how to word what I want to say. It’s not that there’s no chance of any issue, just that I think, based on the majority, the odds are in favor that there won’t be any issue. Alternatively, Glowforge isn’t going to leave anybody unhappy with their purchase. So, in the end, where it matters, you’ll be very very happy with the machine.
So, @mpipes, I had all of 30 seconds yesterday evening to quickly put my square on the lid. I must say I’m surprised to report the lid itself is bowed. I laid the square front to back and noted a wobble. The square’s big so maybe I was touching the edge and didn’t see. So I put it across the lid diagonally back-left to front-right, ensuring I was on the glass only (not the edges). Definitely bowed. But my understanding, as you also stated, was that the lid itself was supposed to be flat. I didn’t get a chance to take a video, but mine is decidedly not flat.
Any other owners care to validate with their lid?
UPDATE on the above…
Yeah… Turns out my lid is flat. And my square? Not so much!
@dpruitt, regarding your post, I think you should only be a little concerned, but you should mostly be optimistic. As for the actual cause of my issue with this particular machine? Unknown at this time. I got it on Monday and I really haven’t been home since Sunday. 
So WYSIWYG right now. Could be that my lid is warped (it is, but is that the issue?) Could be my camera’s not aligned properly. I have a couple more independent tests to perform before I put this in Supports capable hands. For example, I told @dan_berry and others that I’d test from another outlet. Not an unreasonable test. That’ll simultaneously rule out my outlet and my table. So I’ll be hitting that test as early as tonight.