I don't like it and still bitter about it changing.
Those are your recently used applications. IIRC there are four states an application can be in. If an app isn't being currently used, with very few exceptions the apps in that list are either suspended and and only their state is saved using very little memory or (I can't remember the term - maybe Purged) where all of the application's memory footprint is reclaimed by iOS in a low memory situation.
So they don't need to be closed, but they can be removed from that list which removes any memory that might be held for them (if they are suspended). The exception would be an application that's allowed to "run" in the background. I would consider that app to be closed when removed.