I've been playing mandolin like this for nigh-on twenty years!
As a guitar player, the first time I saw a mandolin up close I asked if I could have a go and how was it tuned - GDAE - so I turned it upside-down, thought EADG and suddenly all the guitar chords on the bottom four strings work.
Since the neck is narrow, I've rarely had a problem with reaching or fretting notes on the higher strings. I play some celtic, some American old-time and some bluegrass without problem.
It gives me an instrument I can borrow in a session event when there are no lefty guitars.