Arg - sorry to hear of probs with screens on some units shipped from Amazon. Try your local Best Buy - most of the ones around here in Seattle have stock anyway. Maybe there was a bad batch in Amazon's initial shipment?
Worth persevering - I picked one up at BB today and the screen is absolutely perfect. Totally even lighting, background is lightest I've seen on any e-ink reader. The clarity of the text on this thing just blows me away. (loved my old PW and didn't think Amazon would surpass it - they definitely have) I like the lighter weight and smaller size, the "feel" is great - even fits better in my jacket pocket. Didn't think I would use the bezel page-turning, but it has become my favorite thing about the reader (ok, next to the screen). Very well thought out. Xmas came early this year, for sure