I like the adult covers, actually. I find them simple and to the point. I probably would have chosen them if I had been given a choice. Didn't even know they existed for years.
While it boggles my mind that they thought "people won't know what the Philosopher Stone is", I can't be too hard on them renaming it that way. The French first book is, well... I hate the translation :P I don't blame the translater, only the publisher, who obviously asked him to dumb it down. So, first it's called "Harry Potter Goes to Wizard School", then you have several scenes simply cut off, and you have added explanation about how "in wizard school, there are houses"...-_-'
It just annoys me how people assume children = stupid. So they're going to be given lots of weird wizard words and concepts that don't actually exist, but still the publisher thought "they won't understand the concept of houses, we need to add an explanation on how it's a weird wizard stuff!"
How, and the French covers suck too. I do like the American covers but overall I think the British adult covers are my favourite. It's a shame they don't have a real pocket version. The only one I saw advertised "almost as big as the hardcover!" well, no, that's not what I want, but thanks :P