I was happy with a set of P4s I had on an '04 Chevy (Malibu) Classic for three years and 30K miles. Can't speak to treadlife, since I traded in the car before the tires had a chance to wear down.
Pros:
Price if you wait for the right deal.
Combination of smooth ride/handling. This is where the P4 really shines. Maybe the best such combo I have ridden on, for an ordinary sedan-type ride. When you turn, you know you are turning---but on a flat highway it's quite smooth. Thumbs way up here.
Winter traction. Well-above average for an A/S the first two winters and above average the third winter. Not quite as good as the Hankook H727, (especially in "slush") but a close second among A/S tires I have used in winter.
Wet traction: Very good in heavy rain that runs off the roadway, but be careful when driving through deep puddles. The grooves in the P4 are not as deep as in some other tires. (Might be just personal observation but I suspect it's true.)
Dry traction: Excellent. See "ride/handling" above. This presumes close to normal driving on a standard-type vehicle. It's not a performance tire, if that's what you want. I believe the H-rated version of the P4 was discontinued, in fact.
Cons:
Fuel economy: Not terrible, but I took just enough of a hit to notice when the P4s were installed. Might have been the new tire-factor, but it stayed like that for 30K miles.
Warranty: Note that Pirelli requires rotations every 4K miles to maintain treadlife warranty. That's the most severe rotation requirement I know of.
Manufacture: As of 2009, when my set was installed, some P4s were made in China, if that's a concern. Three of the four tires in my set were made in Brazil, the fourth in China. Guess which one of the four picked up a nail and a slow leak, then wore down more than the others....might have been a coincidence.
I think of the P4 and the H727 as first cousins. They have much in common. The P4s lean a hair more toward performance and handling, giving up a wee bit of winter traction and ride comfort. (though the ride is quite smooth, the H727 is even better.)
The H727 sacrifices a bit of handling and wet traction to provide stellar winter traction and ride comfort for its class and price point.
Can't have everything....but yes, I recommend the P4 for most drivers and applications---especially if it's on sale.