I bought the P700 with the stencil tape a couple years or so ago. I played around with it a bit, but never used it to mark any knives.
The labels are definitely a "one and done" sort of thing. My biggest issue, as loffman points out above, is that it does have a low DPI, so that small font definitely comes out as pixelated.
Is it functional? Yes. Is it to the standard that I'd want for a customer's knife? No. I suppose it'd be handy for marking personal tools and the like, but I'd probably just as soon use it for printer regular adhesive backed thermal labels and such.
If you want to see the pixelation, you can see my Instagram post here:
I showed a zoomed in and zoomed out photo of something like a 6pt or 8pt font, if I remember right. At first I thought it was pretty decent, but the more I looked at it, the more the pixelation started to bother me. I played around with some settings and whatnot, but could never quite clean it up enough for my liking.