If you want the latest (read bleeding edge) kernel that the Ubuntu developers are working, then have a look here:
Be sure to download the 3 files matching your architecture and install.
I am currently using 2.6.37-rc3-natty which will be the kernel that Natty Narwhal (11.04) will be based on. It just works, everything is detected and there is a noticeable increase in responsiveness.
After a brief time with Karmic (10.04), the laptop was upgraded to the beta of Maverick. Everything works out of the box with no additional tricks necessary in getting the Dell Studio XPS 1640 fully functional.
The only drawback I found in upgrading from Karmic was the loss of fglrx as a xorg-server driver. Maverick is shipping with the 1.9 version of xorg-server which is ABI incompatible with what fglrx is compiled against.
The exact error is:
undefined symbol: savedScreenInfo
which causes X not to start.