Now imagine if all the carbon on our biosphere combines with all the oxygen in what was the ocean before it boiled away and all its hydrogen was lost to solar wind.
I'm not sure it'd be exactly like Venus (we have a magnetosphere, at least) but I am sure it'd be very bad.
You don't think having a ground temperature above the boiling point of water would cause any problems other than the release of oxygen from the ocean? How would you get to that point?
Of course, we'd be long dead before that. There's plenty methane in the ocean to drive up temperatures before it combines with atmospheric oxygen (driving them up a little bit further in the process).
I'm not sure it'd be exactly like Venus (we have a magnetosphere, at least) but I am sure it'd be very bad.