The AI could do a much better job at building up its planets. Their planets often have no manufacturing plant. You'll see them with one Lab and multiple Mines. Or other odd mixtures that don't make effective use of the Research, Trade and Mining queue fillers.
Actually I'd suggest getting rid of the Research, Trade and Mining queue fillers. They cause a lot of extra micromanagement when you research an extra planet build slot. I'd instead have completely built up planets build transports or troopships.