Freezing. Horrible horrible freezing. every few hours a freeze. I think 1.4 resolved the freezing for good and 1.8 resolved the game loading issues for 90% of the games..
Uhm the freezing of wii games was solved in 1.2. Also it was solved for 100% of the games.
If you were still experiencing freezing problem that was probably media related (of which they did improve compatibility along the way)