I have just completed the first playtest of Star Fall. This was a combat only playtest.

Expectations: 

1. Inertia rules would require major reconsideration and reworking as they were not expected to work reasonably.
2. Combat would move faster due to movement not being considered an action and attack commands could be used at any point during movement.
3. Damage formulae and stats would need major revisions.
4. Certain stat rules would need minor adjustment.
5. Combat damage and hit would need adjustment.

What happened:

1. Inertia rules worked well almost out of the box and only required minor adjustment, to my shock. They may need further adjustment, but they generally work well. It did take some time for players to get used to them, and they still feel strange.
2. Combat did not move faster! In fact, I realized a little bit late that combat resolution was nearly impossible with existing rules! I was able to fix that relatively easily, though.
3. Damage formulae and stats need moderate revisions.
4. Certain stat rules need major adjustment.
5. Combat damage doesn't scale with level. Playtesters seem to think this needs adjustment in both combat damage increase and level scaling.

I'm really happy my inertia rules weren't intrusive into the gameplay, and they actually made it interesting! Players are already thinking of ways inertia can be used tactically in combat!