Sorry For The Belated Response
This thread is a year old, but I only recently became interested in the RDX.
Dan, yes the t/b does get dirty in a couple of places due to the fact that the engine vents out the top via the valve cover and into the intake tract. The gases pulled out of the top of the engine include oil vapor. This makes a mess behind the throttle blade and can plug the idle air bypass. (rough idle results)
So yes it needs to be cleaned. Easy to diy if you are in to that, if not, let a trusted mechanic clean it.
I say trusted because you will never know if they did not do as promised, until it starts to idle rough (~100k mi.) unless you pull the snorkle and look at the back of the throttle blade.
So a year later and maybe another 10k mi., are you and your wife still happy with the RDX?