I would say battery life issues are not uncommon with specialized hardware. Particularly with Apple laptops, you will find many such issues in the Ubuntu forums. But the good news is usually you can tweak and adjust your laptop performance until it gets to pretty normal.

For example, with my Macbook Air, currently I get about 5 hours in OS X. With similar usage, I found I got about one hour of battery life on 11.10.

But it turns out 11.10 has some power management issues due to the 3.0 kernel. Supposedly 12.04 would fix that and I had a couple other issues anyway, so I upgraded to the alpha version. After that, I got about 2 - 2.5 hours. Then I learned about laptop-mode-tools (given how useful people find this, it's amazing this is not part of the default install for laptops...). Now I find I get about 4 hours. So I'm satisfied.

I've made a comparison of watts used and clearly Ubuntu is just using more than OS X. At idle, OS X is using 9-10 watts, while 12.04 is using 12-13. Part of it is due to this mysterious "display backlight" issue I'm running into, which takes about 2-2.5 watts.

Update: Here's more info about laptop-mode-tools. This is the website for it. From its FAQ, if you want to check if it's running, type cat /proc/sys/vm/laptop_mode at the command line; nonzero value means its running. Also, the configuration file is at /etc/laptop-mode/laptop-mode.conf. To read the manual for it, type man laptop-mode.conf at the command line. To alter the config file you will need to do it as root, e.g. gksu gedit /etc/laptop-mode/laptop-mode.conf. Be careful doing that! If you want to disable it, to test your system, near the beginning of the file, you should see the option ENABLE_LAPTOP_MODE_TOOLS with the value of 1 -- change it to 0 and shutdown/restart.