One of the biggest frustrations for me in Wizard 101 is being pulled into a duel, when it is unintentional. The "sidewalks" are small and inconvenient. I think instead of being forced into a duel when you walk by an enemy, you can click on an enemy, thus causing you to duel it. This way we cant get to places faster, and we wont need an invincibility period after being in a duel.
WORLD
One of the available movements in Wizard 101 is jumping, but so far it seems to be useless. But in no way am i saying that jumping should be taken out because being able to jump feels normal, but in most places, the jumping is completely useless as it doesn't help you get onto ledges or walls. Also, the jump height should be increased because you can only jump like 5 in. in-game. If the jump height was increased, we could just onto small ledges or walls to help us get to places faster.
QUESTS
The quests are amazing, but they could use some help. I think that in your book of quests, it should say which quest is the main story quest, that way, players don't venture into long and unnecessary side-quests.
Other than these problems, the game is great functionally, and has a good story along with the gameplay.