I also think it is best to talk to other parents or the gifted teachers.
Our is a one-day-weekly program plus periodic field trips and quarterly presentations (where they present projects to their whole grade).
I have not had great experiences in the DISTRICT; it's very much a status symbol and parents lobby hard to have their children admitted into the program. At our school, though, the experience has been positive. The kids focus on a theme for the year, different theme for each grade level. Last year was Mysteries (they learned forensic science and crime scene investigation, they learned about great mysterious of the world (stonehenge, the Mayan calendar), modern mysteries (area 51, Loch Ness monster, the Red Sea Scrolls); they learned about codebreakers and how to formulate codes, how to research primary and secondary sources, how to parse news reports and test their accuracy and validity; lots of science and math in learning to calculate angles, speed, etc in forensic). The teacher, working with the framework of the theme, does writing and math exercises -- the children are expected to do math that is three-four grade levels above their grade, and to read texts written for early high school (this was for fourth grade). They also spend a lot of time thinking outside the box, they are taught primarily using the Socratic method, and are encouraged to do a lot of expressive creating. What my son loves about GT is that much of what he does isn't right or wrong -- but rather, they are exercises in critical thinking skills, in using information, etc.
Every program is different, but that's how the cycles are for us -- the year previous they studied mythology, and next year the theme will probably be the Renaissance.
I know in Middle School the kids can be separated into math/English GT classes rather than a more global approach.
Joy, mama to Aquaboy (10), Goldilocks (8), Squidge (4)