yeah matt has used one. he has never really said whether he thought it helped him a lot.

i wouldnt be surprised if what we do for normal training and games puts enough stress on the respiratory muscles already and the use of such a device wouldn't make much difference, but research is always good, and i have also wondered about it... but considering the results i had with simulated altitude training, ie, bollocks-all, i havent taken the time to try it yet.