I thought it was a good episode. It deviated just a little from the regular show format. My five year old pointed out that there was no Sid invention (or Super Duper Uper Big Idea rather).
I think it did a really good job presenting honest and age appropriate information regarding vaccinations. There were times I thought it was just a little too preachy. For instance saying that by getting a vaccination is basically doing your civic duty - that was a little much for me.
In my mommy circles the reviews are mixed. I know quite a few moms who were a little upset about the message since they personally have chosen not to vaccinate. Other moms were thrilled to have someone encourage their children to actually get a shot. I won't get into the debate of vaccinations for me personally, but I can see both sides. As with any children's show, if there's something addressed that goes against what you believe or do in your own home, use that as a platform to discuss your beliefs with your child. That's not a bad thing.