I have a 2012 PP and my friend has a 2011 base w/automatic. He made the comments to me that mine felt more connected to the road. Also, he said it felt much faster. I am sure part of that is due to his being an automatic. Coming from an RX-8 I don't feel the ride in my PP is harsh at all.
At $2K list the performance package is a bargain when you consider all it gives you. For someone who wants a decently handling Mustang without losing any part of your warranty it is great. In that scenario the only good reason not to get one is if you don't want to drive a manual transmission.
Good luck in your search.