Solar Spot forecasts etc - don't be surprised if you are unable to talk to anybody for extensive periods of time (60-100-mins).
Poor GPS coverage.
Always good to know that there is a string of commercial airliners going 'polar', also knowing that there is a good chance of being unable to talk to ATC - which is meant to be pre-requisite for commercial ops?
ICAO & Authorities slow to address the issue so good luck and the odds of reaching your destination are still in your favour ;-)