As long as it doesn't get soggy it's fine. For decking I'd spend the
extra for plywood. There's too much chance of water on floors.

I used 1-1/4" T&G OSB flooring for our house (Don't recall the brand now).
It's strong and doesn't have voids like plywood does. They also put some
kind of coating on the sheets (wax?) that repels water nicely. Ours was
exposed to rain for 3-4 months during construction. The water would bead up
on top and we would just sweep it off each morning.

I'm sure long term water exposure would cause rot, but you would get that
with regular plywood also.

OSB doesn't hold nails well, either, so it's iffy for sheathing.

I used CDX plywood for our roof sheathing because it's slightly stronger
than OSB, and because it's lighter and was easier to carry up to the roof.

I also used CDX plywood for our wall sheathing, because I wanted a rough
sawn face for simulated board and batten (even though we decided not to
install the battens). I didn't care for the look of the textured OSB
plywood.

Otherwise, I usually use OSB and CDX interchangeably. OSB is usually
cheaper, so I tend to use it where appearance isn't an issue.

Anthony Watson
Mountain Software
www.mountain-software.com/about.htm