@xpect: Your 1280x1024-resolution is ideal for Amiga emulation as that's 4*320x256.
I didn't really know about transparent scanlines when I voted "NO" in this poll. Now that I tried it I'm quite impressed by the look 25%-scanlines deliver. I'm torn between screenshot 7 and 8. I think 7 comes the closest to how Turrican II looked on my RGB-capable TV in the nineties.
@Mogilny: Only pics 5-8 have scanlines (1-4 show different upscaling algorithms without scanlines).