Stagecoach have improved their Gold service 66 between Swindon and Oxford. It now operates generally every 20 minutes in the morning and evening peak and half hourly between times.
I suspect it is aimed more at people going to Oxford in the morning and back in the afternoon as there is a one hour gap in Swindon departures between 17:15 and 18:15 - while there are four from Oxford between 17:10 and 18:15.
I have caught this service a few times. At ^6.50 return (valid all day) it offers good value compared to the train on price (train fares vary between ^43 anytime day return and ^10.60 off peak day return). Given the bus goes right into Oxford City centre the time difference is not so great either.
The buses also have wifi.
The relaunched service - which includes four new Gold branded vehicles - was being promoted in Swindon's Wharf Green today.