Well, I just bought a whole new XPS 13 and installed Ubuntu 12.04 Precise Pangolin 64 bit. But I was having some problems like the brightness didn’t worked as I expected, single tap that used to click made me a sad guy and Touchpad scroll weren’t working. But I love to know that there are people who love to solve problems that quick. I would like to thank to Kamal Mostafa who has been contributing us for the Drivers/Kernel patch for XPS versions.
As your touch and most of the things weren’t working, Mr. Mostafa has spectacularly developed kernel patch for us. To solve yourself out try the following steps.
Open Terminal and type sudo add-apt-repository ppa:kamalmostafa/dellxps

Open Terminal and type sudo add-apt-repository ppa:canonical-hwe-team/sputnik-kernel
Then update the repo sudo apt-get update
I would prefer synaptic from now because it shows the lists that I want. So, please open synaptic.
To install synaptic: sudo apt-get install synaptic
Now run synaptic and sort the list by Origin
On the list you see LP-PPA-KOMALMUSTAFA-DELLXPS, select the one and you will get a list from the added ppa.
Now click on every updates that are required on the list of that ppa. And enjoy the show after a restart.
By default you get 1 Finger scroll. To get two finger scroll, goto Settings > Mouse and Touchpad > Touchpad and select 2 Finger Scrolling
Enjoying XPS with fine brightness Up/Down, TouchPad, Scroll.