Dear Stardock,
You gents rock, thank you very much for this new beta. I am enjoying my game as the Iconians. There is much improved in the game compared to Beta 5.3.
However, I have noticed the following:
- Shipyards are taking me 35-75 turns to build. Really?? Is this WAD?
- Diplomacy seems screwy so far. Thalians declared war on me for no reason whatsoever, refuse to even speak to me, and yet our relations are given as "warm".
- Have noticed a few typos, e.g. capitalization where it shouldn't be, but nothing to have a cow about 
Haven't tried to load a saved game yet.
Update:
Further bugs:
- On loading a saved game, every one of my planets/shipyards/starbases has a green shield over it, yet I have NO ships orbiting these things (I saw this bug in 5.3 too)
- 3 columns of the Colonies tab are still screwed up (carried over from 5.3)
Thought I would report these issues, anyway.
Cheers!