Especially the serve tape. I feel the instruction in the tape contradicts with most modern serve techniques. I feel the motion of the serve in the tape is very rushed partially due to the extremely low toss. No momentum was build at all for the serve. You don't see any explosiveness from the serve motion. The only suggestion for power was to only use 75% of your strength, without mentioning anything about racket drop, knee bent, hip rotation, etc. Another difference on the serve motion from modern serves is that he steps into the court with his right foot after serve, so there was no push off from the ground, therefore lacking another element for power.
If you are a true beginner, this tape may help a little. But if you are looking for improvement of your serve, you may be better off looking else where, such as the serve tape by Bollettieri, or the book by Yandell.
Besides, why are Tom Avery's tapes are so expensive compared to others?