Although it's a fairly busy airport, this one is surprisingly calm. Nice spaces, clean, lots of places to eat. Grab yourself a Fazer chocolate at a shop and get acquainted with Moomin while you wait.
One of the best airport I've ever been. It is not so crowded, no big queues on check in and security control, free WiFi. Also you can find many electrical outlets here.
People at Helsinki are polite and very friendly. This is not the first time that I forgot/dropped stv and someone ran after me to give things back to me :) Btw, Geisha Chocolate is very yummy
Now the cheapest & easiest way to city centre is to follow signs to adjoined train station, buy a ticket & then hop on the first train that comes. Finnair City Bus is a bit faster, almost same price.