Quick clarification… one of the rewards WILL be unique to guild wars, but you’ll get them for finishing first or last (you’ll just get MORE of 'em for first). In other words… a guild can fight every single battle during the week trying to get first… or they can fight one single battle with one member, and they WILL get at least one of the unique reward.
We want to make sure that nobody who participates misses out on the cool stuff.
As for “extra” stuff to do… in every respect, a Guild War battle counts as a ranked PvP Battle… you’ll get trophies, glory & pvp points, and lots of gold for competing… so it’s not so much an extra thing to do as it is an extra way of doing something most players are already doing.
For Guilds who don’t play every day… they’re probably not going to max out their points, but I can’t really think of any guild wars systems I’ve ever played in lately where you could optimize your performance but not play on some kind of timetable. It’s an interesting problem though, so we’ll keep it in mind.