Setting AutoAddDevices to false in xorg.conf is required in order to disable Emulate3Buttons

no, you don't _have_ to use that option, you can use xinput to set the device options, see the manpage.

This is very unfortunate.

I do not want to set up xinput scripts for a simple definition I was once able to just set. Besides, running :
xinput set-int-prop "Logitech Optical USB Mouse" "Emulate3Buttons" 32 0
Does not work. xinput support only integer and nor boolean datatypes anyway (I tried with 8 and 16 too).
As I understand, the hal driven configuration doesn't even use the "mouse" driver which accepts the Emulate3Buttons property, but the evdev one, which does not. There is no clear explanation how can such a definition be set in /etc/hal/fdi/, even not in https://wiki.ubuntu.com/X/Config.

All in all, there should be an accessible option for the average user, like me, to turn off 3 buttons mouse emulation for the sake of playing games, especially when he (like the vast majority of users) already have a perfectly good 3 button mouse. I do not have to learn the hal object model, the xinput syntax and the evdev API in order to do this. This option was dropped in intrepid, and on that basis I beg to differ about the closure of this bug.

We use input-hotplug now (=evdev for mice&keyboards), and it won't be reverted, which means that what you are asking won't be possible.

You need to set "Middle Button Emulation" btw, 'xinput list-props $foo' shows the list of props the device supports...

I think the last response is missing the point of the bug report. The reporter just wants an easy way, using the standard Ubuntu preferences tools, to set the status of middle button emulation. He is not asking for evdev to be reverted.

I am in a similar position: with evdev, I cannot change the autorepeat delay and rate for the keyboard. I would be very happy if xset r rate was made to work again; at the moment it changes the settings that it reports, but they do not affect the interpretation of the keyboard.

Hence, I think this bug should not be marked "wontfix", as the thing being requested is in fact quite reasonable: simply to make the standard configuration utilities work again.

I've figured out the proper way to permanently fix this issue using the documentation from here:
https://wiki.ubuntu.com/X/Config

Create a file named mouse.fdi in your /etc/hal/fdi/policy/ directory:
gksu gedit /etc/hal/fdi/policy/mouse.fdi

Then paste the following in there:

<?xml version="1.0" encoding="ISO-8859-1"?>
<deviceinfo version="0.2">
 <device>
  <match key="info.capabilities" contains="input.mouse">
   <merge key="input.x11_options.Emulate3Buttons" type="string">false</merge>
  </match>
 </device>
</deviceinfo>

Now you need to unplug your mouse, then plug it back in again / restart your computer (restarting X I think may also work).

Using "xinput -list", finding the number of your mouse (usually a number between 0 and 9, represented as <number>), then running:
xinput set-int-prop <number> "Middle Button Timeout" 8 0
Also works, but will not remain if you unplug then replug in your mouse / restart your computer.
So I recommend you use the mouse.fdi file above.