These little cuties cost under 99 EUR and provide you with full access to DVB-C transport streams. Should be perfect for building a multi-channel-recording PVR box based on Linux.
So, I ordered one of them and installed it on Debian unstable. Unfortunately, it didn't work out-of-the-box. The problem is related to the QAM-128 modulation used on DVB-C networks. The current 2.6.11 driver only supports QAM64 properly.
Luckily, there is already a fix. You need to download the latest LinuxTV drivers from their CVS. Also install the Debian kernel sources for 2.6.11, and follow the instructions to replace the built-in drivers with the CVS counterpart. Then compile, install and boot the new kernel, and the card should work.
I did this five minutes ago, and the Terratec card seems to be working fine now. Now to set up my PVR software to support multiple cards... We'll see if Freevo can hack it.