I opted out of DRIP also. The brokerage account managers will begin accruing shares on behalf of their customers a few days prior to the dividends being posted, then customers receive a weighted average cost of what the brokerage company was able to gather.
During periods of increasing prices this is generally good for customers as the average cost will be lower. DUring periods of dropping prices it is normally worse for the customer.
Is this your understanding? Because of this I am not part of the DRIP.