I'm using Ubuntu 14.04. Today the Software Updater asked me to update to the Ubuntu 16.04 Xenial HWE Stack (v4.4. Kernel) because my kernel version will not receive any software updates (LINK). But I am using fglrx graphics driver for which I know that it is not supported by Ubuntu 16.04 kernel. So my question is, what will happen if I install Ubuntu 16.04 Xenial HWE Stack? Does it support fglrx driver or will it get automatically removed and replaced by the new open source driver for AMD graphics?
You will lose your fglrx proprietary driver, so you will suffer lack of power management support and latest opengl support for your hardware.
The battery life of my laptop went from 6 hours to just 1 and a half, and opengl went from 4.3 to 3.3. So it is clear that keeping the old HWE stack is more than advisable (in my case at vivid HWE).