First of all I would like to say that there are a lot of valid points that are highlighted here, whether criticism or support.
When that is said, I myself have played melee characters for most of my gaming life. As PA was, it was undeniably very useful and thus chosen by most melee classes, even though they may not have used a weapon you normally associate with the feat. Thus even bards with above average stats could make use of PA against low AC monsters such as ogres or the like. That was not originally the intention of the feat I think and thus it led to much metagaming or confusion among the players because of the calculations, as has already been pointed out.
In our own campaign I have made frequent use of PA to great effect. I can only say that even though we play in a highly magical setting (and thus even higher scaling from bonuses etc) the bonus you received from the feat at especially higher levels almost became too much. When I could dish out more damage all the time in certain kinds of encounters than the casters in our party it became a bit to OP imo. Not to forget as has also been mentioned that casters may on average do more but on higher levels, you expect the enemies to save most of the time, thus diminishing a lot of the damage, while the damage from PA is a static number.
Though, the way it has been nerfed, may be a bit too much (still need to test it properly)
As some have already suggested I think that a sort of capping should be in place. Perhaps make it capped at half your BA, not doubling it when critting, not letting it apply a double str modifier to one hand weapons such as rapiers and the like etc.
CE I never made much use of as I never was the defensive type. The change,though, seems a bit too "much" imo as most fighters consider their int their "dump stat". That would perhaps make a defensive class such as a dwarven defender even less useful with fewer options to raise their AC, as tanking is perhaps their main ability.
Either way, I think the designers should make CE more attractive a feat to take, as it already in 3,5 was way too underpowered and wasn't picked by many players.