i also think that an eeg is kind of a rough examination.... meaning the answers it looks for or the parameters measured arent that precise. so you find out what waves get produced... so? thats not really that much of an insight.
commercial eeg will get more popular and some will play with them while tripping but i dont expect great things really. i think most devices of this kind are being researched in the hope of aiding people with disabilities communicate with computers and peripherals to live a life closer to normal. as far as i know, so far things arent moving at light speed, but i remember one report of some being used to control a robotic arm, and some to control an electric wheelchair.
now the far more interesting thing to perform while tripping would be an fMRI (functional magnetic resonance imaging). basically it gives a map of the various activity in different brain areas at a certain point in time. however, these are far more expensive, the equipment more cumbersome, and the subject has to be quite still....
it would be interesting for instance to see the various activity in the brain that psychedelics cause. for instance, how come some feel more earthy/ spiritual while others just more light?....