1. It requires a healthy ego. Some people feel like it's childish since it is more like playing games than language learning. Other folks don't like making mistakes all the time.
2. It is great for languages that do not already have documented grammars and/or dictionaries. I believe the Summer Institute of Linguistics uses this method in some areas.
3. It naturally caps out in utility at around CEFR A2 / ACTFL intermediate. While many Americans call this level of proficiency "fluent", it really just scratches the surface of a language.
Regardless, I'm glad you found this method and that it works for you. Congrats!
I view it just a great way to jump start vocabulary and grammar learning and comprehension. TPR will need to be supplemented with other techniques, especially for production of spoken language, pronunciation, reading, writing, cultural sensitivity, social cues, etc. Also, in my experience, TPR has been most effective in one-on-one sessions with a tutor, while there's something to be said for classroom instruction where the student can interact with other students, and something to be said for interaction with native speakers of the languages outside any kind of formal instruction.
So, yeah, TPR is just another tool. A tool which I've found useful for certain purposes, but not the ultimate be-all-and-end-all of language learning. Is anything?