Yes I have and I would highly recommend it. I used one in university as a subject so I have only done it the one time. My thoughts and observations:

1. It is an intense introspective experience so if you have going through something in your life like your wife cheating on you or you murdered someone then I probably wouldn't recommend it. I spent a lot of time daydreaming about the future and thinking about recent fuck-ups. Which was disappointing since I could do that any day, I wish I was more in the zone.

2. Condensation builds up in the tank and then drips, which was super fucking annoying. It is super quiet so the drip sounds so loud. Plus you are not moving so you actually feel the drip hitting the water.

3. You start to get phantom itches after awhile and those are annoying but it went away after a while of not really moving around.

4. I answered survey questions afterwards, they told me what they were testing for but I don't remember the details as it wasn't particularly interesting.

Overall I would recommend it if you have a shot, I have no idea how much these types of things cost.