Not being able to have normal conversations with him distresses me. The lack of remark / response and so on, back and forth. It seems his mind doesn't grasp something the first time it is said. Sometimes it's not until the third try that he gets a handle on it.
He will sometimes look blank, sometimes try to look as if he's understanding everything, sometimes get the wrong end of the stick altogether. Not that the latter matters too much — if I wait a few moments it will be as if no words had passed between us at all, and he will ask me a question about the very subject I've just addressed.
We can still converse, but there are many days when communication feels like pushing the proverbial s**t uphill.