I'm using Carbon now. On Beta3 there was few bugs, but since today on beta 4 theres none that you would see on daily usage. Everything you wrote works.
Battery life was same or slightly better than on stock.
Only things i miss a bit is a fastcharge and hdmi.
Fastcharge will be implemented soon so i dont worry about it. HDMI is not working on every opensemc rom, hope they will fix it someday
But i can live withoout it.
Yes you can go more than 3h on one charge, i had smth like 7h on minimum brightness when i was reading a book :P. (wifi was on in background)