LEFT4DEAD2 installment?

so i got the game and downloaded steam right, quick and easy but to actually play left4dead2 is taking ages i mean its only downloaded 5959.7MB/10,669.9MB and its been almost an hour, is it suppose to take long? i guess its because I've got a few big games installed as well or because I'm using my HP Pavilion but i really don't know. I've also got a mac book pro does it work with macs?