As far as I know, B&H is legit and has been around a long time.
I have bought a few items from them here and there over the years. I always got exactly what I ordered, in a timely manner, at a good price. I have never had any issues needing resolution, so can't speak to how well they stand behind their products after the sell (but I had no reason to suspect difficulties, or I would not have bought from them).