I assume you had it replaced free-of-charge under warranty, and ended up with a perfectly good replacement? Google are very good with replacing Nexus phones bought through the play store -- you get sent a replacement phone before you ship your old phone off.
And if you didn't, you're still at least two weeks within the warranty period ... it's not too late :)
Yup, replaced it and got another defective unit. This was around March or April. The person on Google Play's support line knew what I was talking about when I called about it too.
It was a common / known issue, and others had bad replacements as well. A Google search will show it.
Perhaps a bad batch, or a bad software update was pushed or something.
So I did a full return / refund on the second unit.
I could tolerate a common-crash or some Internet based issue that might "eventually" get fixed in a patch. Heck maybe the Mic issue was eventually fixed, but a Google search shows people still complaining about it in June.
But being unable to use my phone as an actual PHONE made it a no-brainer... I had to move on.