It went pretty well! I just selected the Soldier template in the Player’s Guide. My opening scene was the Fire-Kin scene in the GM section (and that led to other shenanigans afterwards). Some observations based on my limited experience:
Only having 1 phase as a solo player is tough. I stayed away from a party of PCs to start with. I think with only one character, there aren’t as many strategic options with choosing a phase. It seemed to me like you’d always want to go in phase 1, as there was no point to let enemies beat on ya first.
Not having default skills is a bit rough for solo. For example, the Soldier template doesn’t have First Aid, so I had no way to heal flesh attrition, except by rest (or finding a temple or some other narrative way to heal).
Action scenes did move pretty quickly and there was very little overhead for managing my PC and any baddies.
It seems like there’s quite a bit of variability in combat (at least at low levels). For fun I fought the same battle twice and ended up with drastically different results, i.e. the first battle I won handedly, the second I got destroyed.
Overall, I had fun and will solo it again. One thing to note is that I didn’t get to engage with the mapless dungeon, hex rolls, or random encounters, which I think will be awesome for solo play. My short adventure was mainly confined to the city in which the Fire-Kin started burning down houses.
Hope that helps, and let me know if you decide to run it solo as well and any observations you might have.