I think there should be a bar in Wizard101 similar to the exp bar but instead it is the percentage of main quests you have completed in whatever world you are currently working on, or the world after the last world you completed. Also, I think this should be part of your profile, so others can tell if you are somewhere near where they are quest-wise.
I just sometimes wonder if I'm halfway through a world or not. You can count the areas on the world map and see how many you've been to, but honestly, that's not very accurate considering that more areas take longer than others. This would be a neat way to kind of gauge your progress.