Gene was a great host: very friendly, flexible and made me feel like I was home. He even gave me a ride to the airport, saying something like "don't take the bus, it's too long; I'll drive you".
His place is very clean and comfortable (The bathroom in particular is better than most hotels). It has a nice kitchen/dinning room/living room open area. Apparently the wifi is not always great in the bedroom, but for me it worked perfectly.
It is located in a nice quiet neighboorhood, but is within walking distance of the bars, cafés and restaurants in Hillcrest. There is a very pratical supermarket right across the street (open 5am-1am!).
I was travelling for business and went to the san diego convention center every day by bus. You can take the bus from hillcrest to go downtown (all the way down 4th avenue to market street). It is a fast ride, but plan your trip: the bus (#3, 120) passes every 15 min or so during peak hours, but at other times they can be very spaced out or stop early (e.g. on sundays).

This was my first airbnb experience and it exceeded all expectations.

Note: If you dance swing, mention it to Gene