Hey JJ, sorry it's taken me so long to reply to this, I dont know if Theresa's said anything but my Laptop died on me rather unceremoniously so I've not had much internet time! On top of that I fear I'm coming down with a bout of Man Flu, it's a real thing y'know
As for Marty, I wasn't so sure to begin with. I didnt know how I felt about the idea of Swagger only being as awesome as he is due to an unseen force guiding his hand but when I read more and realised that Marty in fact did only little unseen things here and there and that Swagger had free will to do as he pleased I was much more intrigued, and then by the whole situation in general.
I feel like Marty opens a lot of doors and adds in another dimension to an already rich and layered storyline, which took me from 'Why am I still waiting for the boom to drop?' to 'Daymn!' in a matter of Chapters
All in I like Marty and the things he brings to the table. The scene where he briefly took control(ish) for a bit of steamyness with Pixie in the shower was a great example I think of exploring the dangers of having such a powerful symbiote