Well he made the boards for the 2600 and I'm not sure how many people bought them, in comparison to the others. I've never seen anyone discuss it anyways. Btw- composite on a pvm 20l5 looks very good, so don't let it stop you from playing.
If anything, I'll s-video mod it if I can't find an RGB solution within a reasonable time. I actually have Tim's NESRGB board and installed it so I have composite, s-video and RGB. s-video blows composite out of the water in terms of clarity and vividness of color. RGB is better than s-video, but not by as large a margin as s-video over composite. The main reason I'd like to find an RGB solution is so I can run everything through one switch. I also have all my audio going through a receiver so consolidating will help with cable management as well. It's still a nightmare, but every bit helps!