@jingtra: The important parts of the xorg.conf for multiple monitors are as follows:
Identifier "Default Screen"
Monitor "Generic Monitor"
SubSection "Display" # <--Add this subsection if you don't have it already.
Virtual 1280 1824 # <--Change these values to set the maximum size of both your screens put together.
I've also attached the scripts I use to switch the external monitor on and off. Read the comments in those files for more info. Have you managed to install the radeonhd driver from their git repository?
Driver "radeonhd" # <--Make sure this is set in your "Device" section. If X won't start with this set you probably don't have the newest driver from git (or the version you downloaded is broken).
Remote Control: Picked up by xev. Thanks gali!! Many of the buttons are the same as their counterparts on the laptop itself, so if you've already mapped volume, media, and side-of-screen buttons they should work. The two bottom-of-screen buttons aren't picked up by xev though, as gali said. Neither is the act of rotating the screen, unfortunately.
"acpi=off": as tC_Crazy pointed out, this is not a necessary boot parameter and in fact should probably not be used in intrepid. Remove it by editing /boot/grub/menu.lst.
powernowd: With the newer kernel powersaved seems to work far better than powernowd - I've only had it hang once during boot, and that was after a hard shutdown. If you're having difficulty with powernowd I would recommend installing powersaved to replace it.