I'm aware that this is a cheap instrument, but on the other hand it's not exactly rocket science building one of these either, so I have to say that I at least expected it to be remotely in tune, but it wasn't. It's off by 40 cents, give or take, which makes it impossible to play with other intruments. To play it on it's own is okay, since intonation between the different notes is fairly good.
This will be forwarded to my 4 year old and I'll try one of the Feadog whistles, which seems to have a better reputation at pretty much the same price, instead.