4. The decision to develop the 3D engine to support a wider variety of graphics cards and PC systems.
While it was tempting for the team to make the Iron Engine (the engine behind Sins of a Solar Empire) have Battlestar Galactica-like visuals, the decision was made to make the game look really good on the widest possible existing installed base of video cards.
Sins still has phenomenal visuals, even on lower end systems, but doesn't include DirectX 10 support (for instance).
5. The decision not to use any CD/DVD copy protection.
Like with Galactic Civilizations II, Sins of a Solar Empire includes no on disk copy protection.
This left the game open for piracy, but the calculation Stardock had made with Galactic Civilizations II was that more users would buy it as a result of not being inconvenienced than would be lost from piracy. That trend has continued with Sins of a Solar Empire.
Another early HUD variation. Ironclad iterated on the HUD and the overall UI probably more than any other part of the game, knowing it was critical to making the RT4X concept playable.
6. The decision to allow multiplayer games to be saved and restored for later play.
This turned out to be a significant selling point to PC strategy gamers. Many strategy gamers like to get together and play with friends on the LAN or Internet. Nothing is more frustrating than a game being interrupted due to a dropped player or just not having enough time to finish a session.
Having a robust and easy to use save and restore option for multiplayer helped make Sins a compelling strategy game for a previously untapped demographic of PC gamers.
The interesting part is that Ironclad originally implemented this feature solely for the purposes of tracking down multiplayer bugs before recognizing its marketability and gameplay advantages.
A near-final Sins HUD. Expect more improvements in the upcoming 1.1 version.