I thought SF's real strength was run D. And while I agree they can certainly cover receivers, New Orleans didn't exactly have a bad outing against them, despite the last second loss.
SF is very strong against the run, but their whole D is pretty incredible.
The pressure they got on Manning in that game was unreal. I can't remember the last time I saw a QB take that kind of persistent beating - probably Cutler against the Giants last year.
It's still weird that the Giants pulled it off. Usually, when a D gets that many stops and that much pressure, it's a done deal.