Pros: Encourages love of reading and learning enhances self-confidence in verbal and language skills.
In a word - shocking. My daughter began using these videos once per day for 30 mins. at around 9 months of age. Because I was conscious of the ample evidence that suggests attention problems from TV watching prior to age 2 I limited her TV watching to these videos only until age 2 and only for 30 mins daily. That said, because she was able to watch nothing else, they certainly grabbed her attention.
At 16 months, she was reading at least 100 sight words and now at age 2 1/2, she is fully reading -- I mean, READING. She reads books cover-to-cover that are intended for 1st and 2nd graders. I have read negative comments that babies just memorize the words and cannot work through unknown words they encounter. In my experience, this is definitely not the case. For example, my daughter often sounds out words using syllables, such as "Gil-bert" or "Mc-Don-alds" even though she has not been explicitly taught these skills.
Moreover, and potentially most importantly, she has acquired a love of learning and reading at a very early age. She is always asking me what words mean and her verbal skills are extremely advanced for her age. I must mention that she was never "pushed" into reading too early, despite what some critics of these videos may believe. Instead, I believe that I just chose a different option for the 30 min of daily TV that most under 2 year olds see anyway. Now, she is interested and seeks out reading opportunities and books INDEPENDENT of any intervention and even asks to go to the library for new books. Reading at grade level is perhaps the most important predictor of later success in school, and I couldn't recommend these videos more highly to encourage an early start.