IMO, PA is fine when you are actually taking a trade off between damage a chance to hit. The real problem is in the extreme ends.
In D+D, at high levels, many swings a warrior makes are basically a hit on everything except a natural 1. PA allows them to take the extra bonuses and turn it into pure damage with almost no risk. Likewise, some times they may only hit on a natural 20. In these cases, there's no reason not to use full power attack.
PA also allows you to convert high-bonus spells into damage, like True Strike or Wraithstrike. This can also be problematic.
In D+D, at high levels, many swings a warrior makes are basically a hit on everything except a natural 1. PA allows them to take the extra bonuses and turn it into pure damage with almost no risk. Likewise, some times they may only hit on a natural 20. In these cases, there's no reason not to use full power attack.
PA also allows you to convert high-bonus spells into damage, like True Strike or Wraithstrike. This can also be problematic.