My in-laws bought this for my son when he was first born. At 9 months old he's just starting to play with it as previously it was a bit heavy for him to hold himself.
There are 3 buttons which have a variety of functions depending on how many times it's been pressed, for instance by pressing number two it'll say 'two' or 'I'm a happy bear' or play a melody. It's great for teaching kids the basic 1,2,3. It has an English accent and it doesn't have an annoying voice like many other products on the market. There's also a velcro cord so that it can be easily attached to the cot, pushchair etc to avoid it getting lost.
On the down side the centre part is all solid plastic so it's not very snuggly. There is a specific on/off switch and a time out auto-off function which is great for saving batteries, and it is programmed to play a melody a few times first to try and re-capture the attention but at 9 months old my son hasn't yet worked out the art of pressing a specific button, he just bashes merrily at all of them. On several occasions it has turned itself off and meant that my son has then lost interest as pressing the buttons doesn't do anything unless you get the heart shaped one. It would be better if it would turn on again when ANY of the buttons were pressed thus keeping a younger child's attention.