Alternate timeline differences:
Jack is a charter boat captain and has an emphatic Minnesota accent.
Daniel is still an Egyptologist, but times are hard and he's making a living teaching English-learning classes.
Sam works in the Aerospace department where her genius is unrecognized.
Sam wears glasses.
McKay doesn't have a lemon allergy
Major Davis has a mustache
Robert Kinsey is President of the United States while Henry Hayes is Secretary of the Interior.
General Hammond is only a Brigadier General
Cheyenne Mountain doesn't house Stargate Command because they never found the Stargate. Rather, the "USAF Advanced Research Institute" (which can be briefly seen on the shoulder patch of one of the guards) is in charge of the program.
Apophis has a beard and mustache.