I have an OpenBSD 3.6 machine as my home firewall. I also have a mini-itx machine with IDE-CF converter card waiting to replace it. This is the state of play
The new firewall box is now bootable to OpenBSD 3.6. It boots from compact flash to mfs.
Waiting for a second IDE-CF converter - the H instead of the V (connectors horizontal instead of vertical - so I can shut the case).
Waiting to get a few missing packages installed - then it will replace the old box. Can't wait. Much much quieter :-)
Currently running an OpenBSD box as firewall on an old slow desktop box that's very noisy. Thinking of changing to mini-itx format.
Probably:
Note - I'm intending to use the fanless Eden CPU rather than the C3 fanned CPU. The box has a small fan - but - if this is noisy I can replace this with a quiet fan.