Tried searching, I know the search is broken, but I couldn't find these mentioned.  They seem pretty obvious though, so forgive me if this isn't new.

For the Advent starbases:

1. The meteor attack does no damage.  At least, against pirate corsairs they don't seem to do any damage.

2. The base doesn't shoot plasma bursts unless at least 1 plasma upgrade is researched.  This may be a graphical thing, I can't tell if the damage is being done or not, but you don't see the balls of plasma shooting out unless you've reserached at least the first tech upgrade for them.