STAFF PICK: Carlisle Floyd's 1970 operatic treatment of John Steinbeck's Of Mice and Men wasn't the finest composition performed in Tucson last season, and individual contributions on stage or in the orchestra pit may not have represented absolutely the most spectacular musical artistry of the year. But as a package, it was a compelling, gut-wrenching show demonstrating that Arizona Opera is now capable of almost anything--even doing justice to a (gasp!) living composer. The company can do equal justice to the more usual repertory, too. Consistently high artistic standards and occasional courage in programming--that's what it takes to make it to the big time, and Arizona Opera is there.