I haven’t experimented at all (yet) with any mind machines, but I have experimented quite a bit with many different audio entrainment products. Like many things, your mileage may vary since the effectiveness probably varies person to person. And, I don’t think these products can ‘instantly’ put you into a desired brain state in a matter of minutes. But, I can say that over time you can definitely make a distinction between the various states (alpha vs. theta vs. beta) and some products do seem to work better than others.

I’ve personally tried the following:

* Brain Sync by Kelly Howell (I would highly recommend these)
* Hemi-Sync by Robert Monroe
- These programs might be too “new-agey” for some, but over time I can definitely tell a qualitative difference in states (like the difference between Focus 10 and Focus 12)
* Holosync by Bill Harris
- I would highly recommend Holosync, however many people are turned off by the marketing hype (myself included). Actually, let me restate: I highly recommend the Holosync “protocol”, not necessarily the product itself. There are some other free software products out there than can basically do the same thing that holosync does (See http://gnomad.info/abyss.htm)
* Software-based products like Brainwave generator and Neuro-programmer 2