I don't think GRRM has brought too many people back to life (it was Beric who traded off with what's left of Catelyn and then Gregor, kind of) but he does use possible character deaths as chapter cliffhangers too often. edit: I guess there are a couple examples of people we know (not assume) to be dead still being alive like Aegon (he's a fake, though) and Mance.
Yeah, the point was more about all the cliffhangers implying someone has died. Or instances showing a corpse we're supposed to think is someone, or someone long believed to be dead, etc etc. Overall I just don't really believe a character is dead anymore.
I do feel like at some point Martin will actually kill someone important off and it'll be a shock - but only because no one really reacts because everyone assumes that the character will just be back in a few chapters.