The patch reduces the CPU clock speed + voltage draw while being idle, reduces the vfs_cache_pressure value at idle, and "pauses" some greedy processes which suck a lot of battery juice while idle which theoretically shall increase battery life pretty good.

The patch also bumps the CPU to a higher CPU clock/voltage profile (or any Kernel-Power profile you want) directly when the phone is unlocked, resumes the processes that were paused while being idle, and resets the vfs_cache_pressure to 100 again.

Simply, your N900 will relax while being idle, and turn to ferocious beast once it's back on.