Using my membership from my local science center, I visited this place as I had free access through the ASTC passport program. I checked it out to see if it was worth taking my kids the next time I visit San Jose. I would definitely bring them back because they would be the perfect age.
From the outside, the facility looks huge, but I realized when I went inside, a good portion of space is dedicated to the IMAX which I did not go to. The museum portion is smaller than expected, but still a decent size. I was quite impressed with the number of high quality interactive exhibits for children, which is great, because it makes it much more immersive. Of course, the BodyWorlds portion is probably the one exhibit that needs a fair amount of explanation before entering, and only parents would know whether their children would be ready to see it.
Overall, in terms proportion of high-tech hands-on exhibits, it's probably the best children's science center I've been too (maybe due to the high number Silicon Valley sponsors?), but certainly not the biggest. Can be quite costly, so I'm glad they are part of the ASTC program. I would definitely take my kids here. I only spent 45min walking through, but if I had my kids with me, I can easily imagine being there for 2 hours to try everything.