Sums either any groups or your friends wishlists up into a nice list ordered by the amount and naming the people who want the respective game.
Likewise, it is possible to check who of your friends/who in a group owns a particular game. This option is offered once you're logged in and suggests the names of groups you are part of. Alternatively, you can click 'Who owns this?' next to wishlisted games.
All modern browsers capable of running JavaScript, especially socket.io, are probably working.