Played 36 holes at Patapsco Valley, a long mostly wooded course with plenty of opportunity to air out your discs. I threw the Inertia on every hole to learn how it flies.
The course was crowded and I was playing solo, so several groups kindly let me play through. The Inertia's beautiful straight-down-the-fairway flight elicited quite a few favorable comments.
General impression: At my distance, the Inertia flies like a faster S-FD. Both discs do a remarkable job of holding the line that you throw them on before finishing with a mild fade. The Inertia is faster than the FD, so it needs less height to do its thing. This makes the Inertia and S-FD a wonderful pairing. From what I have read about the Crave, it should pair similarly with the Inertia.
On a couple of downhill throws the Inertia held the line for 2/3 of its flight and then kicked into a late turn. I will be interested to see whether I can replicate this late turn consistently.
The Inertia opens up some flight paths that I did not have before. Patapsco #2B short is an uphill low-ceiling tunnel with the basket set on the right side of the fairway. I have never been able to get within putting range because of the low ceiling, but I got close today by throwing the Inertia on a low anny.
Another Inertia flight path came in handy on Patapsco #1C. The elevated basket is set on a wooded slope behind a baseball backstop. With no room to run up I was able to throw a ~300' line drive approach that cleared the backstop before fading and skipping under the basket. I do not think I could have executed this shot with the Tern or a fairway driver.
I have not yet tried the Inertia on high anny lines, but I hope to squeeze out a little extra distance by manipulating height and angles. I may also try a heavier Inertia, perhaps in Proton, to see whether changing weight affects the flight.
tl:dr summary: Inertia is a winner. Buy three!