Finnair City-bussi

Clean, modern, convenient buses that leave at regular intervals from the airport and from the city center. The cost is only € 6.30 one way, which isn’t that much more than a regular bus or the newly constructed train, and the advantage is that you get a smooth ride back and forth, where any stops along the way are brief and hardly noticeable. When there’s no traffic, this is the fastest option back and forth. The drivers are helpful and speak English, and on the bus, there’s free wi-​fi. Highly recommended.

I don’t have anything to complain about this service. If you are coming from/​to downtown Helsinki and the airport this is the easiest and fastest way.
For only € 6,50 (regular buses cost € 5) you will be in your chosen destination in aprox. 30 min.
The bus is clean and has free WiFi to entertain your journey.
The times are very convenient, and it takes half of the time of a regular bus. (If you still want to take this route on a regular line bus aim for 615).