I have played about 10k hands at $25PL. I was initially (about 2 months and 5k hands) beating the game for over 20PTBB/100. I then started doing more reading, including this forum, and increased my aggressiveness - pfr gone from 4 to 6, aggression factor increased on all streets. VPIP remains at 18-19. I now win about 8PTBB/100.

I think this comes from the increased ratio of calling stations at these micro limits. Continuation bets from a missed flop with AK are less likely to get away with the pot. Preflop raises don't reduce the number of people seeing the flop as much as they might. I think the pfr is still important - but following up may not be as lucrative. I am going to try betting less with a missed hand and see if I can increase my win rate. Of course at such a small sample size I may have just had some beginners luck.