I too have been playing around with happycube's software in the past couple of weeks and have it working well enough on a VM through VirtualBox on my i7 machine. I've had to use an old AMD64 system running Xubuntu for capturing due to the hardware limitations of my main system (no PCI slots!), but have been succesfully capturing from my CLD-2950 for several days now.

For what its worth, I'm using a Compro VideoMate with the required CX88 chipset, and its capturing just fine. It is a basic non-tuner model that uses the generic linux CX88 drivers (not that it matters; I had to blacklist the driver from loading to get the cxadc driver to work!), I just had to change the vmux setting to 2 whilst loading the driver from the terminal.

The biggest problem I encountered was figuring out the correct dependencies to get the software to run and I'm sure I'm still missing one or two. I'm also unsure as to whether there are more parameters I can set from the command line to change decoding options as thus far I've been trawling through the encode scripts to figure out the basic variables I've been using. I also had to edit the Makefile to allow it compile on my i7 without the AVX optimisation because my i7 couldn't use them through the VM.

Despite the lack of clear documentation, that I'm sure will follow in due course, this software provides exceptional results. The output I'm getting compared to the composite on my player is detailed and sharp, although I am still having a few chroma issues. Multiple captures with averaging soon irons those out, though!