I'm using a 3GS and I've actually found the battery life pretty good. I've been using it frequently throughout the day too because I'm off right now and because it's still new to me (just got it at the beginning of the month). When I return to work soon I won't be able to use my phone much during the day. The battery will definitely get through my work day.
Usually through my pc overnight. As for battery the 3gs always lasted me a day, so this is better then that. As long as i get a day without charging im happy.
Wall charger is connected to my first gen dock. Currently using my original iPhone and when I get my iPhone 4, it will be able to fit in the same dock - so perfect for me!
I normally use the computer/USB route because I have 2 laptops sitting next to me all day. If I have to charge it fast for some reason or have to charge it overnight, I use the wall charger.