Re:
Hired a Cannondale Scalpel from Freemotion in Gran Canaria earlier this year. Didn't think that the brakes would be back to front / didn't occur to me at all.
Belting down from road from the start point, pulled over to the layby to meet up, thought i'd see how well the lefty tracks under hard braking, fist full of BACK brake, skidded into the layby like a child. After that it took me a while of chanting to myself "left is front, right is back" to get the hang of it. Dropped it in a slow speed corner when i wanted to drag the back brake around a 90 degree left turn. After that it was ok, but i spent a lot of time reminding myself which is which and i wasn't as confident as normal on the drops.
It occurred to me afterwards that if i hired a spesh enduro with SRAM brakes i could have swapped the levers over there and then as they're universal. The XT brakes on the cannondale are side specific. Next time i'll hire a bike with SRAM brakes and get them to spend 5 mins swapping them over.
It's doable, but be prepared to knock it down a notch.