I've been able to make it 12+ hours on 4G without issue. This is with light usage however. Initially though it was much less. I have had the phone now for a few weeks and the battery has only gotten better. Firmware is 4.0.2 .
I had horrible battery life - about the same as you - when I first got this phone. After a few days of suffering, I did a factory reset of the device and started from scratch. This helped my battery life for some odd reason, leading me to believe the battery drain is primarily a software issue. It could be an issue with the OS, or maybe it was an app that was misbehaving, not really sure.
Although I was getting pretty decent battery life (around 12 hours at this point), I wanted more. After the factory reset, I installed Juice Defender, enabled it and set it to the Balanced profile. This pushed my battery life up more towards 18-24hours. All of these times I'm quoting are generally with about 2.5 hours of screen-on time over the period.
For now, I only use Juice Defender if I know I'm going to be away from a charger all day, generally the 12 hours or so of battery I'm seeing is enough if I know I can get to a charger before it drains down too far.
Anyway, try the factory reset to see if that helps. If not, you may want to consider a custom ROM/kernel or, maybe the drain issue will get fixed with the 4.0.3 update that is expected in the near future.
At home I use the wifi. I have the extended battery and am getting between 1% and 2% battery drain per hour when not in use. I also get spotty 4G, so I keep it in 3G and that helps too. I also noticed that if I play a game I need to force kill it when I'm done, otherwise the battery drains quickly. I watch my tv shows when on the elliptical machine at the gym. Instead of using streaming, I load it on the phone and watch it local. I can watch maybe nine 45 minute shows on a charge (like when I fly cross country). A few years ago I bought a US Modular Poweraid battery (3400 mAh) external for extra power of a few of my devices when needed. It actually powers the phone and charges it too; pretty cool.