The floor in the Thrillseeker consists of a bottom layer of PVC, a shorter top PVC layer that you actually sit on which is connected a little higher up on the tubes. In between, there is an air bladder which you keep only lightly inflated. The purpose of the air bladder is only to help displace water to help with the self bailing aspect of the boat. The result is that you are suspended between the tubes - and the boat has almost a catamaran-like aspect instead of a raft-like feel.
To me it provides a couple of advantages - the boat feels more stable due to the slight gap in the hull between the tubes, and you can pass more easily over shallow water rocks. The boat is extremely responsive to changes in direction, which is what you need in a whitewater IK. The thwart seat is also unique - it is an integral part of the boat structure - spreading the tubes and providing rigidity.
This IK is not a barge - it is narrower than most others and has smaller tubes. It is definitely performance oriented and is not designed to smash through holes - which is something only a really loaded down IK can do anyway. The boat has a huge amount of rocker, which makes it more maneuverable and better at going over big drops. Because the boat is custom, it fits me very well. The thigh straps come separately and you choose where to glue them to the tubes. The result is an amazingly snug and secure feeling boat. I feel like the boat is part of me, sort of like a hardshell.
Quality is top notch. Attila, the company owner and boat designer talks to you personally to figure out what you need.
The Thrillseeker is a great boat, and really a great value.