The Nettar is a prewar triplet and should have all the limitations associated therewith. Corner sharpness will most likely be pretty poor, even centre sharpness won't be on a level with a modern lens, and in the 6x9 format there seems usually to be quite a bit of vignetting. Those limitations of the lens are fine with many people; however, you may want to lurk for a postwar model with a Novar, which is still a triplet but likely a better-quality one than the Nettar. It should be easy to find one for well under US$100, especially if you're willing to take your chances on eBay.
I like Nettar cameras generally; they're simple, robust machines that in my experience have good build quality. They're probably the best of the low-cost folders. Just keep your expectations realistic.
-NT