It is your right to clear the final.
Not just your right -- it's your responsibility. See 14 CFR 91.3(a). You, not the controller, are "the final authority as to the operation of that aircraft." Not to mention that if the controller makes an error so someone lands on you, you, not the controller, are the one who gets hurt or killed.
your ultimately responsible for you and your passengers safety.
I flew out of a training tower located at KPDK for many years. New controllers make mistakes as do students. So be responsible.
So as everyone else has said, you don't have to spin around to look at the whole pattern. And, IN THEORY, you're just double checking the Controller, not actually looking for someone at an uncontrolled field that never announced. So yes look, but you don't need to get crazy about it.
All bets are off when you go back to an Uncontrolled field.
Cheers and keep flying safe!
Think about this - who is in that tower? A human being. And what do human beings do? We make mistakes. When cleared for takeoff, make that final check yourself to ensure the approach path is clear and then continue to the runway to takeoff. As stated earlier, if you are not comfortable with what you see, advise ATC and decline the takeoff clearance.
I am in full agreement with the others here in that any unusual or non-standard maneuvers prior to takeoff should be avoided.