As a fan of 'Criminal Minds', Season 8 has been a mixed bag while not as variable as Seasons 6 and 9 or as underwhelming as 11.
There are good episodes such as "All That Remains", "God Complex", "The Good Earth" and "The Lesson", and also some disappointing ones like "Magnificent Light", "Through the Looking Glass", "The Wheels on the Bus" and "The Replicator" (potentially good story arc that fizzles out badly which was a shame), not to mention a mostly decent "Zugzwang" before frustrating with its slap-in-the-face ending.
"Nanny Dearest" is neither one of Season 8's best or worst, if anything somewhere around top-middle. To me there is a little too much focus on JJ's personal life, which, despite the presence of adorable Henry and great acting from AJ Cook, was a little too soap-operatic, not as heartfelt as it could have been and Will is somewhat underwritten. Am still put off by JJ being out of character, overused and being significantly less likable than pre-Season 6.
Blake is still somewhat of a cold and disconnected character, though not as badly as some of the previous episode.
However, "Nanny Dearest" is a stylishly shot and atmospheric episode, as to be expected from 'Criminal Minds'. The music is haunting and melancholic, the pacing doesn't feel too rushed or drawn out and the direction is mostly solid.
The writing is mostly thought-provoking if occasionally a little sloppy (such as regarding the escape). The story is compelling, with tension, creepiness, suspense and affecting poignancy, helped by a sympathetic victim in Tara (the other victims are not as well developed but affecting enough) and one of Season 8's most abhorrently creepy unsubs. The ways that the BAU, whose chemistry is still adorable, they are not underused and they work cohesively as a team, use to solve the case are interesting.
Acting is very good from all the regulars, and matched by a moving Yara Martinez and a chilling Christopher Amitrano.
In summary, solid episode that is neither a 'Criminal Minds' classic or a low point. 7/10 Bethany Cox