Thanks for sharing your experiences, JediMom! (Great name, btw!)
We are going to take our son in for a screening at Quest in March. We're all but sold on them for now, as a place to send the kids. We just aren't sure when. We may try to start as early as the 2013-2014 academic year when DS will be in Kindergarten and DD will be old enough to enter their preschool.
The other house fell through, so we are looking now to move to a place in Lake Zurich. It also has pretty good public schools (Actually, even though their numbers are lower than Libertyville they have a gifted program that starts earlier and it sounds like the are more flexible with skipping.) So the public schools might work there too. Time will tell.
On paper, and from our tour, we do like what Quest has to say. They confirmed that they skip, they are flexible in their curriculum, and I feel in general that they "get" gifted kids.
We'll just have to see how the screening goes and if we still feel good about the school after our second visit.