First, it turned out the original switch had a burnt-out commutator. On the other direction I needed, though.
Second, it only switches composite signals. No RGB or S-Video for you, sir. We are very sorry. Caveat emptor – if it doesn’t say RGB and S-Video on the box, it isn’t.
Oh well. I’ve got a new one now. This is also somewhat automatic. When a SCART source comes on, the TV switches to AV alright. Then you have to go and select the source on the box yourself.

The new one looks better, though. Nice connectors. Simultaneous SCART and S-Video/composite output.