I am having the same issue. When I am Chromecasting, the phone will not wake and I have to hold power to reset, luckily this does not affect the stream. I also flashed 4.3 and did not wait for the OTA.
PS. I picked mine up from Best Buy also. I had to call around and find one that just had it delivered as they are going FAST. I know that a few of the other Best Buy's around me are getting a few shipments in over the weekend.