And I thought Sonic was the only game with a time limit...
The most frustating part you could possibly experience is that there is a time limit to go back to the beginning of the level. You jump on a frog statue and you have to make it to the portal within the time limit. Pretty tedious and if you don't make it in time, your money will drain until you are no more. It is even harder in very hard mode so brace yourself.
As for bosses, they are cool, but a little too crass for their own good. When I saw this wierd plant boss, I was grossing out because he was drooling and he was rolling his eyes. Each one consists of a different strategy, so try to beat it in the time limit.
A great platformer I have to say and it should belong to any enthusiast's collection.