Image quality results have been added to the Canon EF-S 35mm f/2.8 Macro IS STM Lens page.
As always, there are many comparisons that can be made, but I'll get you started with a comparison against a known good lens:
Canon EF-S 35mm f/2.8 Macro IS STM vs. EF 35mm f/2 IS USM Lens
The Canon EF-S 35mm f/2.8 Macro IS STM Lens is in stock at B&H | Amazon | Adorama.