I have read numerous posts from various websites saying that the wizard/sorceror spell "polymorph" breaks game balance. Even Wizards of the Coast somewhat admits that. Sticking to just the core games rules, how do this spell and others in the polymorph spell chain swing game balance totally askew?
Perhaps I am just not creative enough to understand the extent to which the spell can make normally challenging situations trivial.
I'm especially interested in the "loopholes" that appear at different level ranges and would like examples - like how polymorphing into an Avariel allows gaining Fly at a longer duration at CL3 than at CL5 with the Fly spell. Any more examples of overpowered usages of the polymorph spell chain are welcome.