It really isn't as bad as everyone says it is,it can be very fun,and challenging,but not enough that you get frustrated.
The graphics are decent, this is the GameCube after all. There isn't much that stands out here.
The sound, once again, is decent, all the planes use pretty much the same sound set, but this is a minor problem, and you probably won't notice it very much. There are some good techno songs in the game, some that really fit into the jet fighting idea, and then there are some that, just, don't...
The game is pretty fun, to be honest, I found the academy missions the most fun, where you have to shoot your instructors down using just your ship cannon, these are very challenging, and its hard to get the high medals on these. Plane to plane combat is the best part, shooting down bombers and choppers just isn't much fun. Bombing is OK, but not nearly as fun as the plane to plane combat.
Overall, the game is pretty fun, it's not a GREAT game, but its not a bad game either, I recommend renting the game first, as you might be done with it in a day or two. Or purchase it for cheap at COSTCO or another store where you can find it for under 20 dollars. Don't believe what others say, this game isn't bad at all, but don't expect it to be the best plane combat game you will play.