I've carried mine for a few days so I'll add:
I'm unconcerned if they could fit more blade in the handle. I find that on some knives, clothing or anything else can snag the tip of a blade that isn't recessed deeply enough into the handle. Being an adventurers knife, you would not want to be snagging anything on a closed knife.
It's not as pocket-hoggy as it looks. Since the blade spine tracks the pocket seam and the handle is smooth where your hands makes contact in the pocket, it doesn't feel large.
I know the backlock is something Sal is playing with as a design element. I've tried to read and understand all of the concerns the Sal has and how he's addressing them. It is really tedious that so much is going on around the pivot/ricasso that effects the overall blade length. As a note, I also have the Siren. I can use the RJ without hitting the lockbar. On the Siren, every time I grip it, I depress the lockbar slightly enough to feel the blade rattle. The Seki backlock is not as nice (allows a little bit of up/down movement when locked) as the Golden made Siren. Still not my favorite lock style, but I'm giving backlocks a chance again.
Serrations are amazing. My first Spydercos were rescue blades in the 90's. The difference between serrations and a straight edge on something like a zip-tie is night and day. Serrations need almost no pressure, they just grab and pop.
Overall ergos feel great. There is a lot of cutting force concentrated on the tip. It feels light, slightly handle heavy, but also really solid.
So far, it feels like a really solid first iteration. I would not be surprised to see some slight CQI's in a future version, but I think the overall feel and utility is going to be appreciated by most users.