There are several differences in the covert II and the SG550. The biggest is the addition of 2 LED's resulting in better night time pics. At first there was concern of battery loss because of this, but as feedman points out, any loss at all has been minimal. Next is the new case. There has been quite alot of consumer concern with the design of the case for the SG550. The bottom access door does not have a seal. Although there were no issues, the consumers saw it as an issue. The new case for the Covert II eliminates these concerns with a rubber seal around the perimeter of the case. This new seal has laid to rest the concerns over weather proof or not. Also new to the covert II is the addition of a free 2 gb SD card. There are also some other features molded into the case such as a mounting hole for a camera tripod. This allows you to use a tripod to mount the camera where there is not a tree.I hope this answers your question.