Hi,
I can add to what Raffles stated. I've had my PP for 4 years now, the first while I had no status with any airline. I've now made it to Elite+ with Skyteam, but it's a nice complement when traveling with non-Skyteam airlines or when I'm flying domestic in the US ...
I have to agree, the Holideck at T4 is great (and, not advertised very clearly, there's free Wifi .. check the little pieces of paper on the wall).
It's also been nice at TFS ... where they serve nice 1/2 size bottles of good Spanish wine ... away from the holiday crowds.
I'm on the 10 free visit plan, and that's perfect for my level of usage ... this year, I'll end around 8 visits, but between a couple of drinks, free Internet in some lounges and the quietness, it's well worth it. (When given the choice in the US, avoid the UA RCC, and go for DL, CO or NW lounges ... the free booze is a nice bonus

)
Cheers,
GenevaFlyer