I'm a lefty and have shot the R9 a bunch of times both indoors and outdoors. Never noticed any gas in my face.
The safety is typical AR15, which is easily manipulated with the left hand. The two different mag releases are both very easy to use for a lefty. The mag release is same as an AR15.
For the cocking handle, I just roll the rifle over so the handle is pointing up and reach over top with my right hand. Its super easy to do.
The only thing I have difficulty with is locking the bolt open without a mag installed. The receiver is slightly longer than an AR, which puts the bolt hold open a bit further forward, making it a little difficult to reach with my left index finger.