For ATI/AMD Graphics Card Owners only - I recommend that you buy, beg, or borrow a decent Nvidia card, but if you must, here is a possible improvement for the extreme FPS drop issues on AMD/ATI graphics cards, at least on my test system (Ubuntu Linux 12.04.1 LTS AMD64, ATI HD 4770, 4 GB ram, Samsung SSD).
First, I removed the AMD proprietary drivers (FGLRX), if present. In a system terminal:
sudo apt-get remove --purge fglrx fglrx_* fglrx-amdcccle* fglrx-dev*
I then rebooted just in case.
In a system terminal:
sudo add-apt-repository ppa:ubuntu-x-swat/x-updates
sudo apt-get update
Then I went to the Update Manager as I wanted to see exactly what packages were being updated.
I installed everything suggested.
Then I rebooted again.
In a system terminal:
glxinfo | grep "OpenGL version"
....Now reads Mesa 9.0 instead of 8.x.
Basically this mini guide reverts from the proprietary driver back to the free open source (FOSS) driver, and then updates the FOSS driver to a newer version than available from the default sources.
The average FPS is not super, but I think overall the game is more playable than with the 'faster' proprietary driver with its more extreme hesitations in PoE.
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