I've always subscribed to the "buy the card, not the grade" mantra. With CSG, I would say more of my cards are slightly over-graded than under-graded. But I'm buying the card, and CSG graded is still severely undervalued, so that's what most of my vintage collection is currently.
My 1953 Topps Jackie Robinson (below) may grade a PSA 2 instead of CSG 2.5. But I got it for significantly less than what a PSA 2 would go for – and it presents incredibly well in a CSG slab. CSG has the best slabs in the business, IMO.