the website is a bit vague but as you said, the cards look specific and seem to be focussed on packet tracing more than typical security
I'm guessing traffic shaping and ... Dare I say it .. an internet that offers different service to different packets ( saves clogging the telecom tubes with voip traffic)
Not really traffic shaping. They are intended to be traffic monitors, rather than manipulators. While you could use them for shaping traffic, it would involve the cards being able to transmit data themselves, and unless that's changed recently they don't actually do that. The easy distinction is: they aren't network cards. They might look like them, but they don't have a MAC address, and you cannot use them as a NIC. This may have changed recently, but it's beyond the original intention of the card as far as I know.
I guess I am interested in what they would be used for rather than needing the hardware myself. Its pretty top level
WAND, and probably most other people using them, use them for highly accurate passive captures of network traffic. They have a GPS synchronised clock, and they insert nano-second resolution timestamps in hardware. Because it's done in hardware they aren't affected by system loading. Using something like tcpdump will give less accurate results because the pcap timestamp is only microseconds, and if the host happens to be busy doing other things (like writing a file to disk, or processing another packet on another interface) it'll delay the timestamp. You could use them for Snort and so on, but it's only really worth it if you want nanosecond timestamping or if you think loading might get high enough that a normal card will have problems dealing with it.