Very close to the airport and extremely close to the CalTrain station. Literally a 3 minute walk from the door of the house to the platform.
Everything was very clean and there were thoughtful touches such as towels, soap, coffee, water, etc.
Only thing to be aware of is that the great location to the airport does also have the downside of being able to hear the planes. Sometimes they can be very loud, I do recommend bringing earplugs if you are a light sleeper.
Otherwise everything was great!