They're quite a pain if you're flying to the UK. First, both the lounges are in a non-public part of the building which you can only get to if you are escorted from the check-in desk, and then in turn you have to be escorted to the gate when the plane is ready to board.
Then in order to get to the lounge, you have to go through security. That's fine, so does everyone else who uses the airport. But the lounges are in the intra-schengen part of the airport. To get to the extra-schengen departure gates for travel to the UK, you have to go back out of the secure zone, and then in again to the extra schengen zone, passing through passport control and a different security checkpoint. So that's two trips through security.
What with waiting around for escorts, and double the security checks, you won't actually get much use out of the lounge. Perhaps that's just as well, as there isn't all that much in either lounge anyway.
Wifi, TV, chairs, tables, coffee, wine, soft drinks, light snacks are provided. There are reports that at certain times of the day the lounges are just as crowded as the rest of the terminal, but you're paying extra!