There’s a very long thread on this, a number of people are finding the bed has a warp from left to right (usually fine front to rear). Others (the vast majority from what we’ve seen) have perfect beds.
From what had been discussed (I’ve been following and involved in this from the start of the reports), it seems BL had a problem with a batch of beds that snuck by QC. After much discussion, it seems to happen particularly with high bed temps (which makes sense).
I think they may have tested them with PLA and only ran up to max temp as a quick test, so they literally didn’t see it. It’s not normal practice to test each machine for hours in QC, too $$.
BL has acknowledged it and is working on it. It will take some time for them to finalize a fix (usually a bed replacement) as I and others suspect it’s a sub contractor that screwed them.
Personally, from my tests, the warp gets significantly worse when the bed it run for hours at max like for PC (polycarbonate) or other high temp prints. It’s postulated the plastic parts of the bed were not properly annealed when made. There may be other things too.
To check yours, look at this thread (warning, it’s long but there’s lots of pics, scroll and find them). You use a straight edge like a 12" metal ruler and a back light.
If you’re printing PLA and other low temp plastics it may take longer to show the warp, or more likely, your bed is perfect. Please be aware it’s relatively easy to fix with some inexpensive aluminum tape and a bit of your time. Mine is almost perfect now, and I’ll ask for a replacement bed when they get it figured out. They’re a pretty smart group of engineers.
Here’s the thread: Warped bed :( seems like a common QC issue - #353 by anasazi37
If you find yours is warped, read the whole thread. It has lots of help. I posted some tips all in bolded to help people find it (plus I like to shout from time to time, LOL)