I've just set them up to work properly, and after one reboot they literally vanished. Evtest doesn't see them anymore, jstest-gtk is blind too, but lsusb sees them. The devices are Xbox 360 wired gamepad and Logitech Driving Force GT.
I suppose I could have somehow broken the xpad kernel module:
$ lsmod | grep xpad gives me nothing (though I've never run this command before so I don't know what it is supposed to do). If I'm right, then I guess there should be some way to enable it, as I haven't recompiled the kernel yesterday (well, I've never ever done it at all).