I've spent one month at Carina and Robert's place in Pasadena and it has been a very pleasant stay.
The house's common spaces are spacious and cozily decorated. The room is big, with a lot of space for clothes and a rather large desk in case one needs to study or work. The bed itself is very confortable. The bathroom is clean and everything's provided, which I found to be a gentle touch.
Location-wise, it couldn't get better if you're in Pasadena for PCC or Caltech, which are both close on foot. The historical town center is quite far walking (approx. 40 minutes) but very close by car.
Since Carina's been away for a while during my stay, I've spent mostly time with Robert. I really enjoyed spending time with him, and he's made anything possible to let me feel like I'm at home. Carina is extremely welcoming, too, and she made sure my check-in and check-out went smoothly. I had a great time with Luna, the house's dog, who's playful and nice to everyone.
There are only two (minor) issues with this otherwise perfect Airbnb. The first is that the room can be a bit noisy if you like the windows to be open, as one window gets noise from the street, and the other gets it from the AC vents in the garden. The second is that one of the house's rules is that the stove is not accessible to guests (microwave, rice boiler and other things are). For a longer stay, this could be problematic to someone.