Good call on not getting the one with a substantial floor. One big consideration for me is how high out of the water I sit. I'm on my 3rd IK and have test driven quite a few others. If you buy one without enough flotation for your size you will be sitting in the water all day. Tube size and floor design all contribute the the amount of flotation you have. You need to make sure you have enough flotation to keep the boat riding high enough so the water will drain out of the holes in between the side tubes and the floor.
Some of the less expensive IK's on the market will tend to taco on you. If your boat won't hold it's shape when you hit a wave you won't be able to remain in control. Once you loose control the odds are you will end up swimming. This isn't really an issue on flat water. Hull design is an important consideration for a flat water boat. You really need something with a well designed floor so the boat will track straight. If your boat doesn't track well you will be wasting a lot of energy making constant corrections while you paddle.
I'm not familiar with the material used in the constuction of the boats people have posted on this thread so I can't really comment on their toughness. I will say most of the damage inflatable boats get takes place when the boat is being transported. If you just roll up the boat and stuff it in your rig without putting it in a bag you run the risk of putting a hole in it due to the material vibrating against some surface. Boat bags are cheap insurance to keep your IK from sprouting leaks.
You can pick up an IK sized boat bag from Sotar for $41
http://www.sotar.com/boat-options-acces ... index.html
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