Based on a little testing with the new beta, I think the AI might need some tweaks to understand how best to handle and deal with starbases.

  I played a test game against the AI last night on a small map (I was TEC, it was Vasari) to try out the new beta.  I screwed up pretty early in the game and let its Evacuator kill off my free capital ship.  Pretty soon after that the AI had 5 planets and an asteroid to my single planet and two asteroids, and I started frantically building defenses, building up my economy, and preparing to be crushed under a massive Vasari fleet.  What happened next was: absolutely nothing.  The AI left me alone for a very long time, not even bothering to send a token invasion fleet.  I sent out some scouts and discovered that it was building a starbase at every single planet but had almost no fleet -- probably with the cost increases all its resources were going into that to the exclusion of building any ships.  In fact, it left me alone for so long that I was able to build a starbase to defend my homeworld, build a new invasion fleet (this one centered on the planet-killer capital ship), walk a few steps up the military research tree, and finally conquer its most accessible planet, which was undefended (it hadn't even built a starbase there yet).  Once I had that (and a very welcome credit / resource boost), I started pumping out anti-structure frigates, and was able to wipe out three more of its worlds -- each was defended by a starbase with no survivability upgrades, and my structure busters made short work of them.  Its Evacuator was spending this time running from planet to planet to avoid my "fleet o' death".

  To explain the rest of what happened, I should draw the map I was on, schematically:

     2          E
   / |       /     \

1   4  - * - 5    6

  \  |     |            \

     3     M  - 8 --  7

  Here "M" is my homeworld, "E" is the enemy homeworld, and "*" is the star.  The enemy holds E and 6; I hold M, 8, 7, and 5.  4 is neutral; the others were enemy colonies that I wiped out, but that its culture hasn't drained out of yet.  My fleet is at 1, the AI evacuator is at 2.

  While I was destroying the colonies, I built a starbase at the star, between the jump to 4 and the jump to E, and put a bunch of upgrades on it -- full weapons, full hanger capacity (thanks for the buff there, it's actually worthwhile now), a single trade slot and as many armor upgrades as would fit (I think 2).  I also dropped a starbase at the end of the phase lane between 4 and the star.

  What happened next was this: I sent my fleet to 2 to attack his Evacuator.  The AI ran to 4, then continued running to the star (taking the 30% damage and antimatter drain).  Its Evacuator then headed directly for my starbase, which was between it and its homeworld, rather than going the long way around the star.  The whole time, it was being harassed by the base's bombers, of course.  By the time it got to the base, it was fairly beat up, but still (IIRC) viable.  It then proceeded to *try to run away to gravity well .  By this time my fleet was in 4 and moving across the gravity well.  When the AI capship got to 4 (with 30% less health and no antimatter), it was right next to my starbase, which of course started firing at it immediately.  The AI immediately turned it around, and jumped back to the star (another 30% health drain).  It landed right next to my *other* starbase with about 500 hit points, no shields, and no antimatter, facing 6 bombers and a fully armed starbase.  BOOM.

  The rest of the game consisted of a little consolidation and a lot of mop-up.

  So, as I see it, there are two serious flaws in the decisions the AI made:

    (1) A strategic error: It put way too much money into starbases.  Or, at least, it built too many of them.  Most of the starbases I encountered, all but the one at its homeworld IIRC, had no structural integrity upgrades -- against 4-7 structure-busters, those go down in a matter of seconds.  It built a couple missile turrets at one planet, but other than that I don't recall seeing any static defenses besides the bases.  If the AI had built an attack fleet worth as much as those bases, I would have been toast; game over.  Even if it wanted to build defenses, it would have been better off with a honking enormous base at (*) (perhaps interdicting my jump lane into the star, before I had managed to break out) or maybe a few middling ones at 4, E, and 6, maybe augmented with a small fleet, than the scattershoot approach it took.

    (2) A tactical error: WTF was it doing with its capship?  It *knew* that I had a base at 4.  Why did it jump back there?  That was just suicide.  And why did it run past my starbase instead of going the long way around?  I wasn't tracking closely, but I don't *think* the damage output from the bombers was that huge, compared to being in range of a fully loaded starbase.  More importantly, when it jumped to 4, it had almost reached the jump point to its homeworld, where it would have been safe; instead of running a little farther and jumping home, it chose to jump to a gravity well that contained a hostile starbase AND a hostile fleet (although I can understand that "knowing" about the fleet might have been difficult -- I don't remember if it had entered the gravity well by the time the Evacuator left it -- the starbase is kind of a gimme since the AI had just "seen" it).