allows to connect 2 external monitors (one via DisplayPort, second via VGA)
reduces cooling capabilities a bit (mainly HDD)
introduces some noise to VGA signal. This is something you should pat attention at when purchasing: we've got many of these ultrabases at my company and some of them introduce only a bit of it while others much more.
DisplayPort support in Linux
Kernel support for DisplayPort in intel graphic chips using KMS (Kernel Mode Setting) was added by Keith Packard in version 2.6.31. On the userspace side driver version 2.7 or newer is required to use KMS. In order to activate it you need to pass modeset=1 parameter to i915 driver either at boot time or in your initramfs.
When passing module parameter at boot time you need to precede it's name by module name followed by a dot so in this case you would need to add i915.modeset=1 to your boot command line.
To pass module parameter in initramfs simply add it to your modprobe configuration and update your initramfs with update-initramfs command.