Upload & Sell: Off
This lens seems to get incredibly mixed reviews. Some love it while others say its not sharp at all... One review will have me set on the lens while the next one will have me sure I need something different
I bet you found the more negative comments in tester reviews and the more positive in user reviews. I say this because at the extremes of the shift the lens is less sharp and exhibits some CA. The natural tendency of a tester would be to take it to the limit of the shift. In real use you rarely need the full shift, so your results are generally better.
I own the 28/3.5. It's a good lens and well worth the $400 I paid for it. I only have the one, so I don't know if sample variation is a factor. But frankly, I doubt it. If you buy one and decide you don't like it, you can always sell it for what you paid. If you use it for 2-3 years and then sell, you'll make a profit. That's how it works with MF lenses.