In reply to indigo:
Been there numerous times, but maybe not really worth the effort from UK (Cogne and Alps in general or Norway are more easily accessed).
That said, it does about offer the best ice climbing in Finland (at least when it comes to access, amount and quality of lines). Most people rent a chalet from Posio and the drive to the "gorge" every morning... Of course, it's also only about 1.5h of driving from Rovaniemi as well.
As for getting there, a car is needed. For foreigners it's either a flight to Rovaniemi or Kuusamo and rent a car from there... or a night train to Rovaniemi and then renting a car.
There is a really basic hut up for rent at the bottom of the gorge (close to Ruskeavirta), that I've stayed a few times.
For season, generally Dec onwards (but it can be thin at the start of the season) until about late March (when things start to get really soggy and unconsolidated).
Oh, here's some pics of the stuff available in Korouoma:
http://www.rollomixed.com/search/label/korouomaPost edited at 12:41