Yes, I really really like the original Weir better, and when Atlantis launched it took me a while to adapt. I almost think they could've gone ahead and left them as seperate characters with only a few minutes or so of added back story.
Quick stab: "Dr. Weir is returning to Washington to oversee <blank>. This is Dr. <new> who the <acronym> has chosen to lead the Atlantis expedition." followed by introductions.
I'm sure some other commenters can explain the reason for the switch.
Oh, and some of the generals in the White House scenes were real generals in their normal roles - fending off alien attacks!
"Celestial body: You put Uma Thurman."