Nope, have not taken delivery. In the queue.
My theory is the call for premium is to meet an EPA MPG goal, and that mid-grade will suffice. According to a post by a Toyota insider with engineering contacts, this appears to be the case. I agree, today's engines with knock sensors and variable valve timing should be able to adjust for 87 octane. Now, if putting it to the test, such as pulling a trailer on the pass out of Denver to SLC, or today in Baker, CA, then yes, probably a bit of premium.
ME try it?

Well, easy does it, especially on a vehicle the price of the LC.