Outstanding episode, the best of the new season by far. Glad the spousal cheating was at an all time low and finally some Joan storyline. I certainly hope she holds her own and doesn't end up leaving - I fear Harry's ultimatum may include buying out Joan's partnership from her. Harry's always been such an asshole to her. He's not a very nice person in general.
I love Joan and have said before one of the tragedies of both the show and the era it is set in is that someone as smart and capable as she is gets thought of as "just a secretary" by virtue of an accident of birth.
That being said, Harry's got a legitimate point. In most partnership business models, the rainmakers get to be partners, not the administrators. It doesn't matter how competent you are managing things, male or female. You need to bring in business. Partners divide the income. Income is generated by bringing in and keeping clients.
Harry does that regularly. Joan did it once. While he certainly deserves scorn from the viewer for how he treated her over the script readings, under the standard partnership model, he deserved a partnership more than she did.