I've only used one product. It is sold by the Immrama institute I believe & the one for meditation is called "Insight".
I've only used it for about 3 weeks so take what I write with a grain of salt. I don't know if I've found it superbly beneficial but it did relax me greatly & I fell asleep (common result I've heard...) while using it.
Insight CD
I also made a copy (extracted it to lossless...maybe not effective but anyways).. for my husband who found it helpful for him & he is in a warzone right now so I suspect that stands for something
I did order Holosync's demo CD but the price was a big turnoff for me so I researched & took a chance with the Insight CD which was a lot less.
If you're curious you can also check out this product:
Neuro-Programmer 2 Home - Self-Programming with Brainwave optimization and Psychological techniques (Hypnosis, NLP, etc)
They sell a program for relatively cheap where you can make your own entrainment CDs...use your own music (so you don't have to listen to what they make you listen to... the Insight CD's utilize rain which is nice..but not all the time...)
They also have a forum on that site which discusses quite extensively all kinds of entrainment products from Holosync to Insight to their programs.
I hope this has been helpful for you. There is also another thread on the Spiritual forum on this site that discusses some stuff too I believe.
Good luck finding something that works for you!