DA* 16-50 is softer at f2.8, for sure, I don't think any copies of it will be hugely sharp wide open. Its not soft at 16mm or any focal length when its at f4 or higher. It slightly exceeds the Tamron 28-75 in sharpness at f2.8, and kicks its butt at all other fstops, so its not like its actually a soft lens, but it is more expensive.
The contrast of the lens however is off the scale. If anyone is thinking of buying it, don't get all hung up over sharpness at f2.8, its a brilliant lens. It takes jaw dropping photos, I can see why some people even complain that its too contrasty, its like a overprocessed jpeg from a P&S compared to other lenses if you process them the same way.
If you want sharpness at f2.8, you might have to go to a faster prime and stop down.