Same issue for me - already reported here. MBP 8,2 with hi-res screen updated to Maverics.
Failed at approximately 35 months after purchase. All the same symptoms.
Sent it in to the Apple Repair Depot for the $359/repair (all told after tax and shipping) and got my machine back with new Logic Board and newly replaced RAM. They said after the board was replaced, it wouldn't boot so they switched out the ram and then it worked.
I got my old chips back (16GB) and never bothered testing them as I needed to get to work.
Computer worked fine and as normal after the repair. No Issues at all. I ran some Graphics and CPU stress tests and the heat never got much above 90C for the CPU or 75C for the GPU. Fans never spooled above 69% or so.
As some have said, I have been very worried that the board would fail again -- but after the 90 day warranty. I can stomach one $300 repair if I am for sure going to get another 3 years out of the computer. But with all the reports of repeated failures, I just don't have very much faith.
So this is what I did -- sold it on Craigslist. Full disclosure given about the repair and the Apple Warranty. Got $1000 for it which is probably fair considering the market for these has gone down since this issue has surfaced and it has been flooded with them for sale.
I bought a new (october 2013) 13" Retina off the refurbished store page with apple care for $1700 after tax and shipping. Hoping to not have the same discrete card issues (since that only has the integrated card) -- as I never edited video, rarely did anything that required high pressure GPU usage. Net loss for me for sure but at least I know I'm good to go for at least 3 years. And I'm sure I'll be able to sell it at that point for half of that.
It may just be that Apple products (if you choose to use them) are becoming more disposable -- which is totally lame and terrible for the planet and checking account -- where you know you will only have 3 years of quality life out of them at which point it's time to dump them on the used market...upgrade to new hardware for a discounted price...rather than keep the machine til it's worth nothing after 6-8 years and buy brand new at that point. Let someone else take the risk of buying old used equipment. For me, I need my computer for work and I need it to work always. That's why I prefer OSX -- over the past 3 years, since this nonsense, i've had under 10 system freezes/lock ups and have had the computer not working properly for a total of about 2 days. Compared to my old Sony Vaio Z, that was miniscule -- that computer was constantly freezing up (3-4 times weekly) requiring full reboots and loss of data -- in addition, I had to ship it into get serviced 3 times in 2 years with many days of down time in addition for hardware fixes that I did myself. And that's not to mention the many ways in which the cheap plastic/carbon case brok and cracked. I'll take Apple 3 times over before I'd go back to that -- but it's becoming a begrudging choice.