I was happy with my onboard graphics but I wanted to be able to run some games in this machine from time to time, so I bought a GT630 1GB DDR3 VRAM. When I boot into Windows everything is fine, gaming performance improved considerably. Consider this is a cheap card but still far better than my onboard GPU.
Now the problem is when I'm working in Ubuntu. From the start I noticed a suspicious behavior of the Unity Launcher. It's easy to tell that the launcher animation is dropping frames (animation with my onboard GPU was very soft). The most bothersome thing is that Flash Player based video players, including Youtube, are dropping a lot of frames, easy to detect by eye. My onboard GPU played them fine when in Linux, including 1080p content.
Driver: Gallium 0.4 on NVC1
Ubuntu 14.04 64 bits
When possible I prefer to accept the drivers the OS loads by default for a given device. I'm not expecting the same performance I get in Windows but less performance than with my onboard GPU has no sense.