It's story isn't complicated, but it certainly isn't boring. Strawberry Marshmallow has the certain charm Azumanga Daioh does (another favorite of mine, I own all four volumes), with it's witty humor and sense of sarcasm.
The art is something I enjoy most, and Barasui certainly renders the characters as adorable. Their faces come off as round and the cheeks are often pink. All in all the artwork is pleasing to look at, as it's anatomy and perspective is usually correct. The only problem is that early on in the series the art is inconsistent at first because the author hadn't realized it would be a series until later on. It also improves greatly throughout the series, and the style changes a bit from early chapters, as it happens often.
The characters in Strawberry Marshmallow are all unique and have interesting qualities. Chika is generally a typical young girl, she doesn'tstand out in many way, Nobue is the somewhat easygoing delinquent older sister of Chika, Miu is the girl who doesn't have much sense and is always saying random and odd things out of the blue, Matsuri is the timid crybaby, and Ana is the English girl who is quite self-conscious about her last name.
The one certainly questionable part of Strawberry Marshmallow is the prospect that the author is, indeed, male. And the idea of an adult man drawing these young female children in situations that would seem revealing (panty shots, bath scenes, you get the idea).If you can get past that, though, and ignore the obvious "loli factor" of this manga (if you don't know what loli factor is, or lolita- I'd advise you to get a little more educated) then you're in for an enjoyable ride.
