Too bad it's not hardy, but on a whim I picked up Begonia 'Sinbad' at a nursery this spring and planted it in my garden. This is a shrubby grower with beautiful silver-speckled leaves.
BTW the smaller green begonia in front is B. chitoensis, a species from Taiwan that I picked up at Plant Delights last summer. The PDN catalog lists it as hardy to zone 7b, but the one I planted in the ground last year didn't survive even though it was an unusually mild winter. Better drainage may help (my soil has a lot of clay and is rather heavy and wet in the winter). It proved very easy to propagate from leaf cuttings I took before the first frost last fall, so I'm trying it again. The plants aren't full size yet; I don't know just how big they will get.