I had a 50mm shift, and it was never too sharp, but many other users say their samples are good - so I guess your mileage may vary.
One nice thing was the price, I think $300 or thereabouts.
For what it matters, I did a test with my P45+ vs the Nikon D3x and a 24mm Nikon shift; viewed on the screen the Nikon was subjectively sharp, but in fact the Mamiya outresolved it by a wide margin. There was simply no contest that the MF system was *far* better.
Edmund