My expereince with Mystery Science is that it feels very doable by teachers and therefore science is sometimes taught because of access to this curriculum. Students also enjoy the videos etc, especially Mytery Doug. Having said that it also loses student interest because the same exact format is used over and over.
Mystery Science is NOT totally aligned to the new standards There are definitely gaps in the learning students attain using just Mystry Science.
If you are looking for instructional materials, check out EdReports which is reviewing science mateials to determine whether it is meeting the standards.