I have just purchased this high chair, and found it pretty straight forward to put together, but really struggled to try and collapse it for storage! After a quick internet search, i found a kiddicare video on you tube (search chicco happy snack highchair/kiddicare) demonstrating exactly how to collapse it and pop it back out again, and now it's a doddle! If you rely on the instruction manual alone, it'll take years and an engineering degree to work it out!!
The highchair itself is great, I'll admit I have no frame of reference, as it's for my first child, but my sister in law has the chicco polly which is a monster. Being short on space we opted for the happy snack version, and it looks pretty good, does what it's supposed to and my son seems comfortable in it. Also it seems to have plenty of room for him to grow, and I get to put all his feeding paraphernalia in the basket underneath.