Well, it was Shell tank residue from an older station, which I no longer use.

 

ok, so i went ahead and opened mine up. This was done at 13400 miles. I got the truck when it had like 2500-3000 miles on it. So for the 10,000 miles i have owned it, i have used shell gasoline for about 9000 of it and BP for the other 1000.
The filter is quite clean looking. The part that might appear as "gunk" is just where the filter was smashed by me when i was cutting into it.

 

That's very similar to how mine looked. My camera was having a bad day.

 

I really wish they had a filter bowl type of setup with some kind of cartridge filter. It would make changing the filter very easy.