Hi Anthin,
I ran Steve's DX10 fix for quite some time, but didn't upgrade to his latest release. I only fly FSX now days to beta test my current work(s) in progress, but most tweaks apply across the board for P3Dv2 and FSX/DX10. Haven't had a go at Steam yet...too busy, but I'll have to add it to the system before I release the new stuff.
Have you tried converting your .dds files to 32 bit? The light poles and other narrow round objects struggle with anti alias and dithering. 32 bit renders more smoothly and gets along with fine details better than DXT5, DXT3 or DXT1.
I'm using only 32 bit texture maps for my current work. The biggest difference can be seen in the LM maps for objects like runways and buildings. This is more significant in P3Dv2 using HDR lighting, but also applies to FSX/DX10.
Most people shy away from 32 bit due to file size, but for my money the increase in rendering detail and smoothness is a fair trade off.