As a travel agent, I would caution you that if you encounter trouble with your flights, PL is notoriously difficult to work with.
Usually the bit you save is not worth the nervousness and aggravation that may occur if you have delays or cancellations.
I also found them very difficult when dealing with a car rental (it was my first time renting a car, and I had no idea that debit cards were not accepted when renting locally; I had to really fight to have my purchase refunded as PL was claiming it was my own fault, like I should've known automatically the rules that car rental agencies follow, rather than that caveat being made clear when renting the car through PL).
I've only once had a good transaction with PL, and that was when I was renting hotel rooms in Vegas (I got a really good deal for my parents' hotel room, which ended up being a suite at a very low price). Otherwise, they're just not worth the potential headache.