I just updated to 14.04 from 12.04 and graphics performance was a bit choppy/sluggish (AMD/ATI Mobility Radeon 4xxx). There's so much information and advice about what to do in this situation that I felt lost, so I just decided to go ahead and try installing the fglrx drivers.
I did this from the software center and now every time I boot there's no display.
I've got a relatively low-powered HTPC running Ubuntu 13.10, sporting a Radeon 6450 for graphics acceleration. I'm using the 14.6 beta of the proprietary (Catalyst/fglrx) This machine is presently used for:
I've noticed very poor streaming performance in Steam, and tests with other devices on my network suggest that the problem is that Steam can't leverage hardware decoding on my 6450.