Hey there, brand new member of the forum and new owner of a lionSTEEL ROK here (the titanium and damascus version). Disclaimer, I'm far from being a knife expert, I'm merely a knife enthusiast, and I'm not a native English speaker, so if anything I write seems weird/incorrect, please feel free to ask for clarification!
Design / finish: the knife is absolutely beautiful, and the design is really well thought in terms of details. One detail I especially appreciate is the rounding of the back of the blade, which makes it really comfortable. It really feels super sturdy in hand, and the ergonomics are wonderful.
Blade: this blade is thick af and super heavy, which makes the action less snappy than with other knives, but produces a really satisfying strong "CLAC" sound when locking. I haven't used it enough yet to have an opinion on edge retention and toughness though. Also, my experience with the blade might not be relevant at all to the M390 version, except for the thickness.
marrenmiller
could you elaborate about the heat treatment issues you've seen? I just know they rely on an external company for heat treatment (described
on their website), which doesn't mean it's worse or better, so I'd be curious what's been your experience with their steel.
Lock: when I received my knife, the lock was really super strong. It pushed too hard on the blade to let it have a smooth action, but maybe it's just a matter of taste. I emailed lionSTEEL to tell them about it, and they offered me to send it back to adjust it to my liking, which I didn't do because France went into lockdown in the mean time. Anyway, I ended up fixing it myself, and now the knife has a pretty smooth action. The "rotoblock" on the lock bar is a also nice feature to prevent the lock from disengaging by accident (even though I think it's strong enough to never disengage by itself unless you're severely beating the knife).
Pocket clip: I personally like it, but it has pros and cons. It makes the knife extremely enjoyable to hold as it removes any hot spot from the handle, but it makes the knife hard to put in your pocket with one hand as you have to push the button to make the pocket clip appear all while holding the knife and sliding it in your pocket.
I hope this helps, let me know if there's something else you'd like to know.