As expected, the intel_idle driver includes ATM-C4 and ATM-C6 CPU power saving modes in kernel 2.6.36, even if your BIOS doesn't announce them. Check it out!
I'm sure it'll lower your power consumption by at least 0.5W on average loads. Of course there might be no difference at all if your BIOS already supports them. But often the BIOS disables the states when the AC adapter is plugged in. They still work, though, when using intel_idle. This makes your netbook less power hungry and more importantly: quieter. For some netbooks this will definitely be a big difference in run time as well.
Let me know how it works for you in the comments.