Silent Subwoofers ie: Buttkicker -your thoughts?

I am a huge movie fan, and have finally completed my theatre room. I have one final question, does anyone out there have any experience with the 'silent subwoofers' such as the Buttkicker made by Berkline. They are generally used to mount to a chair or couch and shake without making any noise. Their purpose is to make your couch feel like it is rumbling when a volcano erupts or when a building blows up.

Are these things for real or are they cheap gimicks that are useless???
Its very easy to use too much with the tactile devices. Used correctly , it can be effective on theatre . Its a balance between xover and output and positioning under the listening chair . You must also be careful how you isolate the rest of the surfaces touching the floor. That said , its fun when implemented correctly.
Cheap Gimicks.

If you want to go to the next level for home theater you need D-BOX motion seat platforms. After selling and designing high end home theaters for 10 years it was my first ah-ha moment.
Steuspeed . Yes, you are correct , the D Box is a one of a kind product that delivers. I see prices have come down considerably from their astronomical levels so maybe its time to revisit them . Good tip.
How much does a D-Box chair run at these days? From what I saw on thier site, it only works for specific movies?
I use these and with good setup and with volume moderation it is a nice effect. Many tend to set it too high and I could see where it surely would stand out and be very gimmicky. But I've experienced a few setups that were done well and in many cases you wouldn't even know they were there per se. I have mine mounted on a platform beneath the couch and with the platform decoupled from the floor and the effect is seamless for my enjoyment. I did try it mounted directly to the couch and yes there was a time alignment issue in that case. But most people I know use the platform or floor joist mounting approach. To compare an IB subwoofer system to buttkickers isn't fair, to different paradigms etc...

I really depends on your tastes, expectations, setup etc...
One good thing and the reason I bought them is for late night movie watching and wanting some impact without having the sub infrasonics throughout the rest of the house. It works perfectly for me in that regard. I think it's a viable options to consider and try, it's inexpensive enough. The D-Box is something different and much much more costly etc..., really not fair to compare the two IMO either. Again, that's like someone asking about a $500 CD player and getting recommendations for $5000+ reference players.
I know people who wouldn't consider their home theater experience as enjoying without their tactile systems in place.