Pretty much every sitting President since FDR, regardless of party, seems to have attempted expanded executive power in one arena or another. Examples from both sides include Truman nationalizing the steel industry, Nixon's invasion of Cambodia, Iran Contra, Clinton's perverse idea of "Executive Privilage" during the Whitewater investigation, and the torture and extraordinary rendition of detainees during the Bush administration.
If anything, I don't think there has been a gross violation of executive power by Obama yet. Doesn't mean it won't happen...a President's second term is where most of these shenanigans occur. I do find it interesting that Senator Obama ran on a premise of "open government" in 2008. Now, I don't think President Obama believes in executive openness nearly as much.