I had hoped on buying this for my 21 month old daughter, that she would have something that she could both use with us, plus something she maybe could do on her own while we are busy with something (without her deciding to redecorate!).
As has been mentioned the image is visible before wetting (although at their age I'm not sure this is important really), and you don't really get the feeling that the child is benefiting a great deal, apart from spending time with you as a parent.
The pictures themselves seem quite flimsy and thin, I had expected something of a little more sturdy considering the target market, but it is barely the thickness of A4 80g paper and seems fragile. Having said that it still survives intact after a few weeks.
After use I found they dry out quickly, which can actually make it a challenge to get your child to reveal the whole picture before areas start to fade again.
I'm disappointed, but I think it was worth trying - I think my daughter is happier with her Iggle piggle teddy and scribbling crayons on a large sheet of paper instead though!