I prefer Gentoo as my distribution because I pick which programs that I want and manually format the partition using options that I prefer to use for desktops or notebooks. The file system that I use is XFS. I no problems using Gentoo on a notebook computer.

I am testing Sabayon 4 from the DVD disc or live disc and it performs well on a notebook computer. Version 3 did not perform well at all even on a desktop. Just like in version 3 of Sabayon, version 4 also have the same feature while the backlight turns off when closing the lid. The setup is just a little too fast or too responsive, but it is nice. I did not install it yet. Suspend to RAM or S3 (I think) is the least of my worries, but I will eventually work on that.

My system has lower specs than yours, my prefered distros are SuSE or Fedora. They both run smooth with a nice KDE desktop (especially Fedora now) and they don't slow down my system unless updating while trying to continue other multiple tasks. Even without the proper video drivers installed (ATI).

You could always check out the lists on Linux on Laptops and see what people have tested, or even put in your results.