I bought this toy for my daughter who was 8 months at the time. She liked the bright colours but didn't have the dexterity to lift the box, press the squeak on the snail or hold the stackers so that the pop up 'popped up'. She's now just under 11 months and although she's got better at holding the stacker bricks and the case, they are not her favourite toy. They don't stack terribly well, perhaps that's a learning point but it's disappointing not to be able to make a tower out of all 10 for her to knock down. Like most parents I play with her toys almost as much as her and I struggle to find more interesting things to do with these. Perhaps, she will enjoy them more when she reaches the stage where she builds towers rather than just knocks them down.
On the plus side: they're bright, colourful and use different colours, they rattle when you shake them (the pop out going in and out), they have pop outs, you can stack them a bit, they're robust and easy to clean. The box for keeping them is sturdy though that can make it heavy for little people. The negatives; well, compared with stacker cups there's just not much I can think of doing with them. I wish you could twist the pop out so it stayed sticking out...now that would add a whole new fun element.