A lot of large funds trade on the open. This can cause volatility that is difficult to make sense off. So unless there is something very specific that you have your eye on, and it's away from the opening price, it's best to stay out until those large orders are filled.
I usually just leave it unchecked. Auction or no auction, if they can reach my price and my order gets executed, why not? Make sure you use limit order though because with limit order your order will never get executed at a price worse than your limit order so all those open auction volatility won't affect you much but if you use market orders, open auctions that create lots of volatility can result in a bad fill for you.