I had bass shakers in my first home theater. I had real movie theater seats, and each one has its own Bass Shaker hooked up to it. The effect was pretty cool. My theater used to be featured on Parts Express' web site when they sold Bass Shakers, but they are pretty much sold out. My current theater does not have any transducers (Bass Shakers or Butt Kickers), but my new one that I am building right now will have them again.
They are no substitute for bass, but they can add great effect at lower volume levels and really give a "feeling" of rumble. I am using them because when I had them before, I found that people first were in awe over the dedicated home theater (that was back before many people had anything), but when they left they talked about the Bass Shakers being the coolest part of the theater.
This time around, I am using 2 old Bass Shakers that I still have attached to a loveseat that was also in my first theater, and I just bought 4 more new ones off of eBay. I have a 320watt (way overkill) sub amp from an SVS PCi subwoofer that I am going to power them with. They will be mounted under the custom home theater seating that will be built for my home theater (once it is installed, it can't be removed without destroying it)...
Anyway, you can get a lot of effect out of cheaper solutions, but the ButtKicker is a great choice if you have the cash sitting around. Of course a D-Box Motion Chair would be totally outrageous, but for $10,000 - $15,000 for a couch, it is outrageous in price too.
