Well you are right I have nothing to prove and this is totally derailing the OP's thread for no real purpose.
Well this is a fake "opinions wanted" thread anyway so derailing it is completely fine.
I use cased you dont we have established that and we all agree that you need to keep everything cool and good air flow we just do it in different ways.
But just becasue you asked so sarcastically here is a pic of my cab:
Its gone through several incarnations as my needs, funds and ambitions grew over the last 6 or 7 years but its still the same cased PC buzzing away in there.
So you just have the PC sitting at the bottom of the cabinet, unattached? That's another reason I pull for de-casing, it's
easier to mount the PC in the cabinet so that it doesn't move around. This is important for when you have to move the cabinet from one place to another. I don't know if you've ever had to transport a cabinet, but one of the rules-of-thumb when moving a cabinet around is to have NOTHING loose inside the machine, for fear of bits flying around inside causing shorts.
Here's a pic of one of my cabinets from awhile back:

Everything is mounted, bolted, L-bracketed down (including the sub woofer). Don't mind the mouse in there, I was in the middle of updating the software when I took this pic. The cables are also tied-up now as well, and a KVM switch is in there too for attaching an external console. In this case it was a XBOX360 for a little while. This cabinet was finished in '09 and the PC and internals have been running strong ever since.
And yes, of course we agree on the heat issue, but I still don't agree with not having the PC or Xbox de-cased. I can live with that disagreement though.