I bought the red powerbreathe do dah ahwile back and Id say it was worth it. As Grogyrock says it takes a number of weeks for the benefits to show.
However I found that within the first week of using my powerbreathe thingy the quality of breath i took had improved. I noticed that when I got breathless from doing any exercise it felt different.
This could have just been my perception as I was pretty eager and excited to get using it. I had also read up about it so I was aware of what it could do and other peoples opinions and results so perhaps as I said I may have just been imagining this new quality of breath *text deleted*.