I think just keeping distance and range is the biggest difference between KB and mma.

Just watching some fighters who are very good at keeping the fight standing and using their stand up skills effectively - it's like there is a solid object of specific length between them and their opponent.
Whenever their opponent moves forward, they move back, or pivot to the side, using angles, that exact distance - never more or never letting their opponent close that distance.

Looking at their stance - it's like their rear leg is spring loaded, so they can change that distance very quickly, as oppose to the more flat footed style in regular stand up, when there is no danger of a take down.

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Our KB-ing coach who trains some of the top mma fighters in NZ drilled this tirelessly - staying spring loaded on the back leg - always keeping that perfect distance, and using angles.

Alot of the mma fighters in the gym often give problems to the regular kickboxers - even though their kicking/punching ability is not on the same level, due to the fact that their use of range is superior.
They stay out of range - they don't get hit.
They close the distance when they wish to strike etc.
Just a better ability to do this - sucks for regular kick boxers :)

http://nbcsports.msnbc.com/id/22825103/vp/24055920#24055920

I think this fight is one of the best example of a fighters ability to maintain that range through out - although he also has good tdd also.

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Also I'd agree with the explosiveness - perfect whip motion in their strikes - stops them from over-committing to the strikes maybe - without loosing power..

The top mma fighters who aim to keep it standing are all explosive and very accurate.
There's lots of guys on youtube that demonstrate this.

But also a few examples of stand up guys who transition to mma and cannot make use of their skills effectively due to this lack of explosion - Peter Graham from the recent IMPACT FC promotion on OZ springs to mind - as brutal as he can be in regular stand up, his strikes just did not seem to have much effect in the mma ring.

I believe also it's largely the reason why dutch KB fighters transition so well to mma - as they train conditioning and explosiveness very well - as well as very good footwork and timing, possibly due to their points system working more in favor of punches?? - like western boxing.

PS I agree - huge learning can be done from watching - Mike Tyson used to watch everybody.