Install Windows
Using this answer prepared earlier.
Preparation
Download an install ISO of the Ubuntu Secure Remix for 12.10 x86_64. UEFI boot has the least issues with Ubuntu 12.10 and the secure remix has some tools that will be required.
Use UNetBootin to create a bootable USB stick for the installation.
Before you leave Windows, disable acceleration with the Intel Rapid Storage Technology. Don't worry, the cache will be safe if you leave its partition alone. Ideally, the volumes on your mSATA disk should be labelled something sensible like "SRT_Cache" and "Linux", these names will be needed later to identify them.
Install Ubuntu
Insert your installer USB, reboot and press the magic key required for your boot menu (F12 for my Dell XPS 15 L521x), choose to UEFI boot the USB drive. Choose to Try Ubuntu. There are some things that need to be done before the install will work.
Once the Ubuntu desktop has started, open a terminal and change to root and perform the commands from here to get Linux to detect the RAID volumes on the mSATA:
# modprobe dm_mod
# dmraid -ay
# ls -la /dev/mapper/
Note that one of the devices in /dev/mapper ends with the name of the spare volume of your mSATA device, this is the one to install Ubuntu to.
Run Install Ubuntu from the desktop shortcut or Unity bar shortcut. Click through and choose to "do something else" rather than wipe your existing disks (the foolish and selfish default option). This should launch the Ubuntu Installer disk partitioning tool. Choose the /dev/mapper device that's named as the Linux partition and create a partition table, create an ext4 partition to be mounted as root (/). Create a swap partition too if required, but if there is lots of memory, it's probably not required.
Continue the Ubuntu install as usual from here, when done shutdown, remove the install USB drive and power back on. It should boot to Ubuntu by default.
Update Ubuntu with:
# apt-get update
# apt-get dist-upgrade
Install Bumblebee to get the nVidia drivers with Optima working correctly, otherwise the nVidia graphics accelerator will drain all the batteries and run all the fans.
sudo apt-get install python-software-properties
sudo add-apt-repository ppa:bumblebee/stable
sudo add-apt-repository ppa:ubuntu-x-swat/x-updates
sudo apt-get update
sudo apt-get install bumblebee bumblebee-nvidia
Reboot back to Ubuntu.
Fix the boot loader
The Ubuntu Secure Remix includes Boot-repair, run this now, let it detect all the things including UEFI, then click the top button to allow it to do its default repair sequence.
Use your favorite editor to edit /etc/default/grub and set the default boot and timeouts (Windows should be named Windows UEFI loader) and run update-grub.
Reboot, you should now have a complete list of boot options for all the OSes installed.
Restore Intel RST
Boot to Windows, open the Intel Rapid Storage Technology application, and enable acceleration, it should remember its settings and switch back on.
Done!
Best Answer
Dell laptops with an mSATA SSD built in are in a RAID configuration enabling Intel's Smart Response tech to store a cache of the most used files on the SSD. This means faster boot times, application start times, etc. You can upgrade the built in mSATA to a bigger SSD, then go to the BIOS and change drive configuration to AHCI. You would have to re-install your OS but you can then install it on the SSD and use the hard disk as storage. This is my configuration and so far I have been happy with it with 4 second boot times to Windows 8. You really do not gain much if any battery life doing this, but the performance advantages in themselves are outstanding. I would caution that if you go this route, you should NOT install Intel's AHCI drivers as they are not compatible with the hard disk and would cause it to disappear for Windows (not the BIOS). Just use Microsoft's drivers and you'll be fine.