I had time to test it this morning and it seems to work pretty good after quick testing . I can confirm that there is a hyphenation problem with some words. However, it is not a big problem in normal use since the issue seems to be linked to compound words. Here is few examples:
English: Finnish: my input: text-prediction

• text input: tekstinsyöttö: tekstinsyö: tekstin-syö
• shoe rack: kenkäteline: kenkäte: kenkä-te
• (space) alien: avaruusolio: avaruusoli: avaruus-oli

I think that most Finns write compound words separately (tekstin and syöttö) and remove the space later (if they aren't too lazy). If you do that the prediction knows those separate words.

I put the text-prediction for comparison with an Android phone and both predictions were working quite similarly with most common words. Sometimes the most obvious conjugation is among the last words in the list but I believe that will improve after use (in Sailfish).

Also the prediction knows every bad words in Finnish and some name-calling slang words. I believe that it is not a surprise since the corpus was from forum.

EDIT: And I almost forgot: huge thanks for you, tusen tack!