I'd rather sign him permanently, I was very impressed with him last year and actually said that's the type of player we should be nabbing from Celtic as he's in the thoughts of the Australian national team - easily make money back on him as he will never have a career at Celtic.
I agree with the loan comments but let's be honest if we're taking him on loan from Celtic, odds are he will never play for them and if we have an option to buy or quite simply just sign him at the end then yes, it's a good signing.