My early 2011 mbp 15" just started this behavior in the past 2 weeks. Without any real consistency each time (after resetting PRAM, SMC, multiple reboots, etc) I was somehow able to get back in.
Yesterday was a bad day, but I managed to get a SuperDuper copy of my hard drive and then late last night poof, system froze and could not recover at all. At this juncture I just want the pain to stop as I've already been researching used mbp's as well as pc/laptop for a replacement.
This morning was the worst. While googling and youtubing for help I must have tried rebooting and resetting about 40 different times, including using Internet Recovery (cmd + R) multiple times. Not sure how but I eventually got in. I thought what the heck I may as well upgrade from OS 10.7.5 to Maverick. Since the internet OS upgrade appears to occur at the base level with an internet connection, the entire upgrade completed without a hitch. Upon reboot, everything came up quickly and normally.
Without hesitation, I invoked a time machine backup and another SuperDuper disk clone which took about 3 hours total.
It's now been up and running without a single glitch for about 9 hours. I've yet to reboot again as I'm too afraid and I hold my breath with every keystroke/typed. I'm sure it's just a matter of time but this afternoon was a good day for the mbp.
I am gearing up for a pc/laptop replacement as I think it's appalling that IMO Apple hasn't found a fix, issued a recall, or stood behind their product.
One thing I'm convinced about, is that this is primarily a software issue, not hardware. Why? Because upon immediate reboot almost every time hot or cold I get the appropriate gray screen with the apple in the center and the gear turing. However basic, that's still complete control of the graphics in my opinion. It's only after the gearing stops and advances to the next screen to open the system up that I might get a blue screen, stripes, split, scrolling lines, or a simple blank gray screen.
Moreover, this morning when I performed a complete Maverick upgrade via the internet that upgrade process took complete control of all the nice graphics without a single hitch. If it were hardware, I'm convinced I never would have made it through the OS upgrade.
Moreover, since the upgrade, I've attempted to conduct business as usual without a single hitch and not once have the cooling fans engaged. Normally the fans will turn on 10 - 20 times per day over the past 6 months. If anything, the fans should have engaged somewhere during the backups after the OS upgrade as I was transferring several hundred GB's in a very short time while also browsing the internet and caught a video or 2 during the process.
So IMO, the hardware story is bunk. It's either in the firmware or OS and perhaps the Maverick upgrade corrected the problem accidentally.
Before going to bed, I will try a clean reboot or two. But right now I'm just enjoying what I have.