I agree that Annet Mahendru, who plays Nina, the Russian girl that Stan has fallen for, is incredibly beautiful. Marina Squerciati, who played Irina, Philip's old flame and, ostensibly, the mother is his child, is also a beautiful girl. I wouldn't put it past Philip's manipulative KGB masters to have instructed Irina to lie to Philip about a child, in order to test his loyalty. What they did to Philip and Elizabeth before makes it impossible to discount the possibility that Irina's story is as much a legend as that of the KGB thugs who tortured Philip and Elizabeth.
I have really enjoyed Richard Thomas' performances as Agent Gaad, the FBI supervisor who is Stan's boss. Gaad is so ruthless he's scary.
The Americans keeps getting better and better. There is no better written show on television these days and Keri Russell and Matthew Rhys have been perfect as Elizabeth and Philip.