I haven't seen any change in Bradley's defense. Still 110% effort, great foot speed, and mental lapses. The characteristic AB play is one where he hawks his guy for 18 seconds, then turns his head at the worst possible moment and gets burned. If he had Smart's instincts, he'd be All-NBA (as Smart will).
That said, you're paying the guy 8M. He morphed into a very good mid-range shooter. He's a model citizen and the team philosophy is based on defense, hustle, and depth. Seems like a good fit to me. You can pay Reggie Jackson 16m/year, or you can have AB and Crowder for less money.