We did Center for Gifted last year with my two boys, ages 8 and 10. I hate to be negative, but I was not too impressed. First of all, one difference between them and CTD is that they will and do accept almost anyone on "parent rec." They really seem TOO laid back. Secondly, the director, Joan Smutny, is long past the age she should have retired. I am not really saying this about physical age (have known many older individuals whom I hoped would never retire) but I can only assume Ms. Smutny was not always the stereotype of the old grandma next door who just wants you to listen to her talk. Really...not kidding. Her presentations were excruciating.
The classes we had were not wildly challenging by any means - they are short and seem to veer towards "fun." I'm sure by now I sound both mean and overbearing, but my kids actually ate up the 3-hour (1 topic) classes we took at CTD a few years ago. These at CFG were three 1-hour classes that never seemed to really get in depth. Also, we took both a lego robot and a robotic arm type class and no one was really interacting with the kids. They were pretty much left on their own. A computer class was better (and less chaotic since each kid was seated at a computer) but it really wasn't the right level. I especially wouldn't do it for my entering 6th grader... oh, that's another thing. They are very loose with grade levels. Depending on enrollment, they might put 2nd and 6th graders together.
My ds8 took a math class and literally came out the first day and said, "Umm, I think they put me in the wrong class." He wasn't joking or being dismissive... he really assumed that a mistake had been made. We turned around and went in and the CFG was great about letting him switch, but...
Overall, I bet my kids had fun, but I wouldn't consider it "gifted" programming... just a fun class to take.
Sorry I can't be more positive.