I'm running Ubuntu 13.04 on my Dell Latitude E6520.
My video card: VGA compatible controller: NVIDIA Corporation GF119M [NVS 4200M] (rev a1)
When I plug in the HDMI cable for my second monitor, I get a lot of screen flicker. The second monitor works, but the refresh rate is horrible (I get mouse trails like crazy).
For the record, this was not a problem with 12.10, and I didn't have to install any additional drivers with that OS -- it ran like a dream out of the box. I'm not opposed to trying other drivers, just laying down the facts :)
Also for the record, I don't have another type of cable I can try at the moment -- I'm planning on picking one up today, will report back if it helps.
Cheers!