I just ceiling mounted one on the weekend, using the two screws and plugs into gib. It's fairly straight forward to do, except there's a bit of trial and error finding how far in to screw the screws. They have to be far enough out that they go into the slots on the E400, but if they're too far out, the E400 hangs lose with a gap from the ceiling.
BTW, it seems the default for auto channel selection is only to do it on start up. That would mean no adjustment as the environment changes (through neighbours etc). However, you can change it to be daily at a set time. Has anyone played with that? Or are people setting up a daily auto reboot of the whole device or something?