Pros: lots of salts in different colours. Cons: not clear that you need a "jam jar" from the outset. This is a hassle and we don't normally just have them lying around. For the price, why not include a small pyrex beaker? Esp if you then want the child to stir it in a water bath over an open flame! Madness. I found it much easier and safer to use boiling or near boiling water from the kettle, as I could control this better esp as the temp required was only 60 deg and we could do this in the garden.
The instructions I generally thought were poor, and did not include nearly enough useful info, IMO, about the structure of crystals, how and why they grow. Why a seed crystal is helpful. Why do they grow better suspended from a thread? The importance of a saturated solution, etc. Also, not enough explanation of what the petri dishes, etc are for. The diffferent activities were fun useful and varied but could have been better laid out.