The Linux-based incarnations of HPTNF/EFIKA with one-port additional NICs are working quite stable now and with reasonable throughput (ca. 0.4-0.8 of the maximum, depending on the particular NIC and the filtering setup). The best performers tested so far: Intel PRO/100 S and 3Com 3C905C-TX.

Unfortunately, multiport NICs are still a no-no in combination with EFIKA and Linux, at least for now, but we'll see :-)
I'm putting high hopes in the newly acquired RB44G 4-port NIC here.

A more detailed progress report with other goodies is available online at my Efika Projects site.