Silent Subwoofers ie: Buttkicker -your thoughts?

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.