I'm on the night train from Kolari to Helsinki, returning from a work gig. This is the longest distance direct train trip in Finland, covering most of the country. It lasts around 11+ hours with around 900km distance.
I've always wanted to take one of these trains, as most of the train is sleeper cabins. Check out mine!
The train's free wifi doesn't suck either. Naturally it fluctuates as we go, but they appear to have lines from all Finnish carriers, judging how my public IP's owner seems to change all the time.