I'm arriving with my family on 12/26 & staying a few blocks from the Puerta Del Sol subway stop. Is it practical to buy the 10 pack subway tickets at the airport & travel to our apartment via public transportation? Are the transfers between subway lines free or is an additional token required for each transfer? Thanks!

The transfers are included in the original fare and the ticket is a single coupon that is good 10 times. It can be shared amongst several people.

The 10 viajes is 5.80 and a single is 1.15. (According to my 2/05 Plano Esquematico de la Red)

Actually, a single journey is 1 euro. However, if you have a lot of luggage, a taxi or shuttle would be better. To get to Sol, you have to transfer 3 times. And finding an elevator in some metro stations can be a hassle. Imagine my surprise when getting off at Tribunal for my flamenco class that I had to walk up 5 flights of stairs to get to the top!