Previously I was using three PCI boards (BT8x8 & SAA713x) and a bunch of USB Kworld "EZ-Cap" dongles. The USB dongles worked OK, but have not been reliable hardware, over half have died in the 2+ years the system has been running.
The Sensoray 812 set me back $200 direct from them, which was less than I spent for eight of the USB dongles, although it was less painful to add a dongle or two at a time as I expanded the system after the initial setup, it was painful to rather quickly burn through my spares as they failed. Also USB to /dev/videoX mapping is a mess, with it seems race conditions making the device ordering usually change with a reboot
The biggest hassle with the Sensoray 812 was mapping the /dev/videoX entries to the physical connectors on the break out cable as they just sent me a cable that would work, instead of one made for the board, although it appeared to be labled as the "upper half" of their 16-channel board. Unfortunately video input 9 was not /dev/video0
Basically download and unzip the drivers, make, sudo make install, shutdown, install the board and reboot to reconfigure the ZM camera setup.