While I switched from an Samsung Captivate i897, which has a smaller battery then the sgs2, I was running jvs on my cappy *android 2.3.5* versus the uckh7 2.3.4 build, I am still getting very similar battery life of averaging 18+ hours, I went almost 17 hours and started charging at 44% and at home weak signal but the sgs 2 has better signal then my cappy ever did, the call quality is 100x better *considering I was using a i9000 based rom, kernel and modem on the i897*, which was expected since the cappy has the audience chip. But with Autosync on, Bluetooth always on, getting a ton of email and uploading data, streaming music for google music. Similar battery life as the cappy running gb = nice. Even with voodoo lag fix, the cappy still lagged where my sgs2 has not lagged at all and running the same amount of programs. The camera is fast enough for what I use it for and having the front facing camera as well as a flash was a welcome change from the captivate. But considering having a 1650 mah battery with a dual core 1.2 ghz cpu and 4.3 inch screen compared to the single core 1 ghz cpu, 4 inch screen and a 1100 mah battery with similar battery life still amazes me.
HTH,
Charlie