This item has been an instant and repeated success. My little boy is having a lot of pains with his teeth at the moment, constantly chewing on anything he can get his hands on (often his actual hands) to provide some pain relief, but he often gets frustrated with things that can't hit the "right spot". The size and shape of this item, mean he is able to hold and manipulate this round his mouth independently. Due to the materials used, he is also able to chew any part of it, which provides additional flexibility in its use.
I've seen a few people comment on it being "too large", but at 5 months old and on the 25 percentile (so a relatively little, little man), my son has had no difficulty getting it in his mouth (in fact, we first presented it to him a month or so ago with no difficulty then either). It is bigger than a dummy, but it isn't designed to be used like a dummy, so this wasn't an issue for us.
Best of all, when he's been chewing on his hands, he's actually rejected them in favor of this when we've placed it in his other hand (without us having to manipulate the hand out of his mouth), so we feel like he's accepted this by his own choice.