I bought the Xacto set and promptly broke the second saw blade .... Found out they don't flex very much or very well.
This is one of the reasons I would like to also try a really Fine (say 50 Teeth Per Inch) Japanese Pull Saw - far less change of snapping a blade when you're pulling towards you, than when the blade is in compression and it grabs and flexes.
That said, one of the reasons I bought another Zona (which arrived today) is that they seem to flex a reasonable amount - ie: I haven't broken one yet!
D