I asked the same question, or similar, before i bought my first laser. The consensus was a knife that was continuously thin at all points and wisps through food without effort. Or something along those lines. Interestingly, I have seen many say that spine thickness has nothing to do with this. I guess it is one of those things where all lasers seem to have a thin spine but not all thin spined knives are lasers. This makes sense to me as I have many knives that are around 2mm+/- at the spine and they are very different than my lasers.
Regardless, you asked for our experience with the lasers we have. I have a Ginga and Kono W#2 and I would say that they are more comparable than not. Both knives are fairly thin throughout and have a subtle convex, not overly pronounced but enough to make them perform well enough for me. Neither are what I would consider good with food release but they are not horrible either. If we use potatoes as an example, they stick, however a flick of the wrist will free them up. Compare that to something like a Fujiwara FKM or Suisin Western Inox and the difference is night and day to say the least. Misono isn't any better either. Digressing back to the lasers I would say that the both pretty much have that feeling of gliding through food as if it wasn't there in the first place, with most objects. Spongier mushrooms seem to be my only obstacle. Not that the knife does not work well but you can feel the drag almost as if the knife is telling you to pay attention or it will come to a full stop, but never does. If that makes sense to you.
Bleh, more coffee is needed. I apologize for my thoughts not being organized.
Okay, starting again I would say that these knives are thin from the spine to the edge and everywhere in between. Interestingly they have fairly robust tips. They perform well but they are not as thin as some of my sanmai knives. This has never shown to be an issue. They also have some flex, particularly at the front 1/3 of the blade so one must take care to not flex them on the stones. That should not be an issue for anyone with decent sharpening skills as the flex is slight. Speaking of sharpening, my lasers sharpen with ease and more so than any other knife I own. In my case I suppose that is due to a number of factors. First off they are both W#2, they are thin overall but especially at and behind the edge.
Another thing I can say about my lasers is that they came with a rather obtuse angle out of the box. It was almost as if there as not an edge. I mean, they were sharp but I needed to set my own edge. Doing this vastly improved performance, or at least to my liking.
Again, I am sorry for jumping all over the place here. Anyway, I hope this was of at least a little help.
