614-536 here. So about 55%. These stats can be misleading as the lower your average, the more likely you are paired with a weaker player. Probably 15% of these matches end in a default by way of disconnect- many of which are on purpose. Personally,I never quit however it is quite common.
Still, AS is by far my favorite part of the game, the best way to connect with other players, and the main reason I remain active. WGTLS Guilds take it to a whole other level-where you find the best competitors, much much tougher and more competitive than in the 'general population' among the elite tiers.