The field of view of a 35mm on an APS-C camera is about the same as a 50mm on a 35mm SLR - or roughly the same as the human eye. For portrait work many prefer a longer focal length. The old 'standard' was between 90mm and 105mm, so roughly 60mm to 70mm on an APS-C DSLR. Personally I have always preferred something a little longer. With an SLR I used a 135mm, and with the DSLR I am happiest using my Tamron 90mm.
My new Pentax 35mm cheap and cheerful has a maximum aperture of f2.4, but at least it is usable wide open.