The AI ignores PQ 1 planets. This was not a bug prior to Dark Avatar.
Now PQ 1 planets now end up as some of the best planets on the map once you research all the improvement techs (PQ 15-18 or so). This gives the player a serious advantage.
When I play, I ignore all PQ 1s (as I feel like it's cheating to settle them), but I would rather see the AI colonize them occaionally.
Cheers
h