Just finished PoP, and I thought it was a good one time playthrough, in the same way some movies are only really good the first time you see them. You can add my vote to the rent don't buy column. As others said, it just does not have much in the way of replay value. After finishing I didn't feel compelled to do anything else. The achievements were not the "fun to get" variety, they just felt incidental to completing the game.
I don't think you can die, so I see where the comments about it being easy come from. There is no penalty for borking a mini game button masher in a boss battle. At worst, they get some health bar back. The saving grace of what would otherwise be a very dull fight, is stringing together the right combos for the right boss. And perfecting your parry and counter is more rewarding then button mashing too.
The Crackdown style cell shading looks good, and the witty banter between the prince and princess has some comical moments. The guy is a player, and she is a virgin, so it is a tried and true formula being followed.
Time to exchange it for some Afro Samurai hack&slashing, all this games combat system did, was make me long for some.