The sweet spot mechanic really makes it feel like you're trying to catch a slippery bar of soap! The only thing I would add to that is that it might be nice to be able to 'launch' the soap in a certain direction based on where you click it, so for example if you click on the far left, the soap flies off to the right. Might make it just that bit more soap-like!
Making the bubbles at the bottom pop if you click on them is a lovely detail, btw :D