I've used the Powerbreathe regularly over the past month or so but only in the evenings. I found it quite convenient to use late at night but somehow life has been too hectic once I get out of bed. Following a chat with Eddie Fletcher last Saturday at Cardiff (he emphasised the importance of using it twice a day for the first 30 days), I've improved matters a little. I now take the Powerbreathe to work with me when I do my part-time teaching and fit in using it during a morning coffee break.
It's difficult to determine whether or not it is proving any benefit, as I was already very fit (10 British age group records set this year) before I started to use it.
It does make sense to me that in the sport of rowing where the chest is compressed for much of the time any improvement to breathing intake efficiency would be very beneficial. Being forced to breathe deeply and powerfully for thirty breaths does seem to be a useful exercise. I'll continue using the Powerbreathe, and twice a day whenever possible.