The actual game play in Freaky Flyers, I thought, was pretty entertaining. You could replay each level multiple times without boredom due to all the goals they give you to complete. But after a few levels, it gets ridiculously difficult, and the bonuses you get for completely these goals don't make up for the time you lose in doing them.
Maybe with practice, or after trying out each of the characters, it would make a fun (and easier) game, but there was another problem I ran into. The second disc always locked up my game. Adding in the slow load times, I spent more time listening to the loading music than I did actually doing anything.