Spotting the issues alone is time consuming, then explaining how to apply six variations on a single rule to the facts at hand, plus coming up with reasonable policy arguments to change the law so the case comes out "better," when are you supposed to have time to even look at your notes in an exam?
I found that having notes was almost a liability last semester, I kept thinking that I would have time to find something I forgot, but I never did.
The only exception was single question in a multiple choice section that wanted to know who said what in a ALI argument over a restatement rule.
I dread the thought of a take-home exam. There's just no way to convince yourself you've done your best. I know I'd spend every minute I was trying to sleep or eat worrying that I should be working.