I noticed that sometimes the AI even builds too many factories now: I worried a bit about their research and PQ 5 planets with 3 factories and a shipyard are arguable. I usually put a bunch of stock markets and/or research facilities on the very small planets, replacing the factories when all other buildings are done and upgraded. Many factories are much better than the infamous gazillion embassies or farms though.

And they didn't seem to be interested in building the Hyperion Logistics Centre or the Hyperion Shrinker in my test game. It might be that I simply killed them too soon, but I thought they should have built it at the time.
On the other hand I also noticed that some AIs seem to rarely build farms, I think it was the Altarians in my last game.
On a general note, I think a rule "do not build a wonder on a special tile" wouldn't hurt. (Replace another building with it instead if necessary.)
In general, I agree that AI planetary building has been improved a lot. The risk for eye cancer because of total embassy ownage is at an all time low.
My main concerns about the current AI are the following:
(1) It is way too cheap to buy techs for money, especially when having good diplomacy values (so there might be two different aspects involved). I researched maybe one or two dozen techs myself in my last game and bought the rest, the tech tree was finished within 4 years (at very fast speed though). And I think the AI should care more for bad or undecided relations when deciding about tech trading.
(2) The tactical AI astonishes me regularly: It seems to forget to move some ships every once in a while - I definitely look forward to an implementation of the "give the AI all the time it needs" option.
(3) The AI (or some of them) should be more aggressive against races with very little or no military. It's astonishing how long you can survive with some bribes and no military at all. Sometimes the first ship I build has blackhole eruptors.
The planetary buildup problem is mostly out of the way, time to face the next battle!