Has anyone done an overlay update for the default IAH, that will put the various airlines in their proper places, and allow multiple runways to be used? With what's available now, it's just chaos. :)

Yes. Over at PAI, if you download the package which describes how to park aircraft using radius sizing, you will find a KIAH AFCAD with gates identified and sized for various airlines that serve IAH. The AFCAD does not use multiple overlays, but the aircraft will park at their proper gates using the radius method. Two runways are activated.

Thanks. I'll check it out :)

I see one for KIAD, but not for KIAH.

It is not in the unoffical AFCAD section. It is actually posted in the General Discussion forum section under the "Standardized Aircraft Radius Matrix" topic.

Can someone do one for KIAH using the Real Airports payware scenery? that would be awesome ! :)