Having used various cheapo tenon saws (with thick blades and big teeth set) I decided to take the plunge and try a LN "carcass" saw. On the one I've bought I've found that the blade isn't quite true (it's obvious when looking down the blade) - on the concave side its out by ~6 thou in the middle.
Is this realistically an amount that matters ?
Although I bought it for sawing the shoulders of small tenons, I tried it on some 5" shoulders (only 1/4" deep) that I happened to be cutting in some ash and found it hard to cut accurately to the scribed line (*1) - though I'm the first to admit that this could well be due to an absence of skill :)
*1 - my technique, for want of a better word, is to start off cutting on the right-hand-side of the scribed line (I'm right handed) on the far edge and as the cut progresses gradually lower the saw so that eventually it's cutting the full width (I do this to stop it skating about all over the piece when I start the cut). I found that by the time the saw was cutting full-width the blade had crossed the scribed line. Looking down on the saw it's concave on the left-hand-side.