I'm trying to get 100% in A0 and it's incredible hard. 
I had 98,50% and have made dozens of tests - each good of them gave me around +0,10%. It wouldn't be a problem, but each test with even only one mistake took around -1% from my score!
So I spent time getting i.e. 99,60% and then boom - couple of mistakes or even typos (cause I'm getting nervous and angry) throw me back to 97% - even lower than I was before.
I start even thinking I don't need this 100% at all...