I gave mine the brick wall test and found that at 100% magnification, the files show it to be the least bit OOF in the upper right corner, but so slight that I consider it a keeper. I've tested a number of other 35s (Lux FLE, pre-A Lux, Cron v4, CV 1.2, and 40 Cron) the same way, and it's the best for its match of resolution, absence of corner smearing, and zero color vignetting. Some of theother prime lenses are about the same, and I remember my Canon 24-105 was much, much worse in all four corners. So I have about 98% of the advantages of a prime.
As to rendering, the FE is very sharp, very contrasty, very useful, and what I'd call 'modern-style boring.' To my eyes the 40 Cron and even the pre-A Lux offer a more attractive rendering, and are sharp enough especially when stopped down to 2.8: almost as good in the corners, lower contrast, and a kind of roundness-of-forms, in contrast to the pores-and-nosehairs detail of newer lenses. But these are just subjective preferences. I value the 35 FE for the times I want autofocus.