The major AI problem still unresolved in AIC, IMHO is this :
All right, as a preambula, here is something well known to all AI moders:
One of the worst AI' deficiencies is the inability to scrap a planet 
facility to give a way for the one more suited to the global Empire status. 
As an example, take a look at this _truly_ horroble example - 
AI (rock oxygen) colonizes a rock hydrogen (just an example) planet early on. 
Let's assume the planet fits under the "mineral colony" criteria. Fine. 
AI builds two mineral miners and leave this planet in peace. 
~100-1000 turns later AI discovers atmosphric converter. Alas, our planet 
has all slots filled and it will never be converted to oxygen atmosphere.  
 
 
How to make AI be more "intelligent" ??? As it was proposed before, let's  give 
AI a special facility. It must have  the "convert atmospher" value to 
be a VERY long time, practicaly unrealistic, say 1k turns. It' major purpose is to secure 
the planet facility slot and be upgradable top the "real" atmospheric convertes. 
Now, since every AI_construction facility should have "convert atmosphere" 
as a first entry, AI should build this temporaly facility first. Later on, AI will upgade 
this building to a proper  converter and scrap it once conVersion completed !!!
The one drawback is of course that AI builds temporaly  facility whose whole purpose
is to be scraped later on. But that' no problem. Let it produce 
some minerals/something_else for awhile
Bingo, AI will convert atmosphere of every single colony !!  
 
 
none/gas_giant is a problem of course.