Sometimes when I try to get the screen back on (After is goes to sleep) neither the Power Button or the Home Button work or are sluggish, causing a delay before the screen reappears. This started happening about 5 days ago and can be quite annoying. For example, I was on a call and when I wanted to terminate the call, I could not wake the phone for about 30 seconds or so. It seems to be random, and can occur after the phone has been in sleep for a while or right after I put it in sleep (by depressing the power button). The phone seems to otherwise perform as it should. I went into the boot partition and cleared the Cache (which had no effect). It seems to be like when a PC Computer lags because its processor is at 100% utilization and it eventually recognizes the key press. I have an ATT Pay as you go SIM in the phone as well as a 128GB Trans Flash (Micro SDXC Card) in it, which works quite well.
I saw the phone at CES - the tech people at the ZTE Booth recommended this phone and I ordered it from B&H when I got back. I had a ZTE Maven (ATT stock phone) and liked it, but it was lacking in memory and I was only able to install a few apps.
Some pics from CES....