Olimex Active Electrodes and Open EEG

I am considering purchasing a full open eeg setup from Olimex, probably with
active electrodes.

Does this equipment really work?  
Has anyone used it during a relaxation exercise or sleep and compared it to
a  medical grade eeg?  
My intuition is that due to the difficulty of getting a good eeg trace (good
electrical contact, noise, wishful thinking :-), etc.... ) it might be hard
to determine objectively if what is actually being measured is an EEG.  Of
course my intuition may be completely wrong.




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