Got my Z a few weeks back. Adjusted the mirrors properly (which in my case was as far "out" as they go), and not at all fearing the blindspots that were such a concern to me also before I actually had the car.
Now, perhaps they are there and since you can't see what you can't see, I may eat these words some day, but I hope not!
On the left I am using the "lean forward and look back" method just to be sure.
On the right the "porthole" is actually useful as long as the passenger seat is not all the way back. Not sure I'd see a motorcycle or a Smart Car if it was exactly between the rear and right side mirror fields, but seeing normal-sized vehicles ok I think.
Not sure it's the vehicle I'd pick to weave in and out of Manhattan traffic every day, but for most situations I wouldn't let the "blindspots" keep me from buying this car.
Don