I have the same model you have and faced the same dilemma last December. I decided to spend the $340 and get the logic board replaced, because it was a lot cheaper than buying a new computer. My current dilemma is whether to replace the almost-full 320 GB hard drive with a faster 750 GB drive, or not put any more money into it and buy a new computer when this MBP feels truly unusable to me. The reason I hesitate putting more money into it is that it's long had wake-from-sleep issues when connected to an external monitor, which some people say is due to the faulty graphics-adapter issue, but Apple told me that the graphics adapter checked out fine. In any case, my Applecare coverage ended two weeks ago.
I'm still trying to decide what kind of Mac to get when I do upgrade. A lot of what I used to do on my MBP, I now do on my iPad. I use my Mac primarily for Aperture, Logic, video encoding, and any tasks that require heavy typing. I'm leaning toward a 27" iMac, because portability is less important now that I have an iPad. A 27" Thunderbolt display with either a MBP or a MBA is a tempting (if more expensive) option, too. In any case, I'm going to wait until the new Ivy Bridge models come out before I decide. If I get an iMac, I might keep my MBP around as a backup, a media server, or for when I do need portability. I checked eBay, and recently sold MBPs of the model we have have been fetching between $500-600. That's on the borderline for me between "It's worth selling" and "It's worth keeping."
