This is one of the worst shopping experiences I have ever had. I have seen it come in stock several times now, but when I add it to my cart and try to proceed to checkout, I get "Due to high demand, your order could not be processed. Please try again later." This happens every time until eventually I get the dreaded "Oops, we had trouble processing your request. We're working on fixing the issue. Please try again later.", which means that they gave up and dumped it from your cart. (Edit: Actually, no they didn't, keep trying! If it comes back in stock, then spamming "Proceed" may work.)
Now I'm also getting it failing to add it to the cart to begin with, with the message "Oops, we had a problem with your request. Please try again.". At least this is better than two weeks ago where I would get very unprofessional-looking cookie errors. Edit: The icing on the cake (Add To Cart click): http://imgur.com/dHmOL
Google really needs to step up here. Forget missed sales opportunities; this is just reflecting very badly on them, period.
UPDATE:
Possibly the first real feedback from Google on all this: A message displayed at the top of the Play store reading "Google Play is currently experiencing very high traffic. Nexus 4 is not sold out and will still be available for purchase. Please try again shortly. Thank you for your patience." It was up for about five minutes and has since been removed. The Nexus 4 is now consistently in stock, but attempting to purchase it always results in "Due to high demand, your order could not be processed. Please try again later."