Down to 24% in 21 odd hours yesterday, i left background data on, turned sync off, left wifi on and used 2g only with a payg o2 sim. emails, facebook etc i updated manually. used the bus app a couple of times texted a few people and made one phone call. I never left the house though, will try the same amount of use next week when out with my 3 sim (obviously 3g only) and about and post results. Nexus one - gingerbread.