The one bad thing about the Acreans, indeed perhaps the ONLY bad thing about them, is that -1.5 to morale at the beginning. Puts a bit of a crimp in the 100% approval bonuses strategy for the early game. But if one can luck into some Harmony Crystals and/or trade for them, then it's lights out.
Thinking about it, and doing testing on an Insane map seems to bear this out, that approval penalty hurts more on larger maps due to the time it takes to research techs scaling with the number of colonizable planets on a map. It's relatively easy to beeline to approval boosting techs/modules on smaller maps. A bit more difficult when each individual tech takes longer to research.
Perhaps the biggest WOWZA for the Acreans is that their speed boosting buildings are separate. That is, yes, they are Player Only. But one does not upgrade to the next level. Put all three on three separate +3 military tiles (if one has three of them) and then surround each of those with military boosting buildings (if one can clear the tile space [not a given])...
<contemplates for a moment>
Well, Warp Speed takes a whole new meaning!