I still don't have any roof rattle on my ISC.
The only thing I can think of is the carbon build up issue some of the 2010 IS250C's have. But that is covered an additional 8 years on the warranty for that potential problem. I personally don't know anyone that has a sedan or the hardtop that has had to actually do this though.
I go to the dealer for all my oil changes so they can check my car out every few months. I have yet to run into any issues on mine at all. Your wife will love it and talk about bonus points for you! LOL