I can assure you it works, it's not April 1, you just have to follow the instructions exactly, re boot (this means pull mains plug out) with card inserted, press
Sky guide on remote, take card out, re- insert and wait.
I tried on three
Sky boxes this morning and it worked on all three.
I have a
Sky+ with the full EPG loaded with a Boots Advantage card in the viewing card slot! (Not sure if I get any points, though)