As others have said, it depends on what you are looking for.
In a nutshell:
- If you are looking for world-class AF for moving objects, the OM-1 is the only M43 body that can perform in that league. So, to answer your question, if that's what you need, then yes, it is worth it.
- If you are looking for large-sensor high ISO/low noise performance, than no, it is not worth it. You would be better served by using a FF if lower light environments are where you shoot frequently.
The OM-1 sensor does do better than prior M43 sensors in the high ISO department, but it's not going to give you the equivalent low light performance of a current generation FF sensored body.
So, yes, it is worth it and no, it is not

.
I didn't buy one as I already run both M43 and FF, and only very rarely do subject tracking, and I am not a big fan of the Oly UI (although it is supposed to have been improved for the OM-1). So, for me, it would not have been worth it. On the other hand, if I did BIF, I would have seriously considered it.
Horses for courses, you know?
-J