I own the 35 Summarit and it's the lens I use most on my ZI. A lovely, gentle, "clean" quality to the images. Handling and size, build quality are excellent. The one thing I don't like about it is the fair amount of barrel distortion, but I tend to be fussy about this. Others may not care.
Yes, Roger Hicks's review is very good. I gather Sean Reid has reviewed it too, but I haven't seen that.
The big stumbling block is the price, and many would argue that for that amount of money, or less, you can get equivalent or better Leica glass (used) or equivalent CV or Zeiss 35 lenses. I suppose that's right. I bought mine used!