Saw this one on Saturday night with my girlfriend and highly enjoyed it. I think a lot of the people who came out of this movie disappointed thought it was going to have much more action, but I highly enjoyed the subdued, intimate focus it had because of the scale from the point of view of Arrietty and her family. The scope of the setting didn't need to be much more than the house and the surrounding nature and it worked.
Arrietty herself was very charming, curious and inquisitive to tradition and the bigger world around her and makes for a great focal point to the story. Personally I was unfamiliar with Bridgit Mendler (for good reason with her previous Disney track record) but she provided a nice youthful energy to Arrietty's voice.
The biggest moment to me was the scene where Arrietty has to tell Shawn (Shaun? Sean? There's no consensus on the spelling) that her family has to move from the house due to being spotted, but not for her part of the scene. It's the reveal of Shawn's condition which had been touched upon slightly beforehand: a potentially fatal heart problem. That moment significantly changed the tone of the rest of the movie, changing it from a simple account of a week's worth of time through the eyes of a boy to potentially the last week of the boy's life based on the outcome of his operation. Not a small task or easy thing to meld into a G-rated animated feature.
In the end, Arrietty's family does have to leave their home, sailing away in a teapot, but not before our main characters have left a changing impression on one another. It's a bittersweet ending and in a way refreshing to see as much; even with the potential of the dollhouse in the room Shawn stayed in, it is not utilized outside of a few small matters and in any more standard ending would've resulted in our borrower family being able to stay and residing in it, as it was originally built to house them before they were even known to truly exist.
The Secret World of Arrietty may not be as epic a tale as some of Studio Ghibli and Mr. Miyazaki's earlier works, but it is still beautifully crafted and differently subtle compared to most modern movies. I'd say that the purpose of Shawn's trip to that secluded house sums up the experience of the film: a peaceful retreat from the harshness of modern life with just a sprinkling of magical wonder.
Stand firm for what you believe in, until and unless logic and experience prove you wrong; remember, when the emperor looks naked, the emperor is naked; the truth and a lie are not "sort of the same thing"; and there's no aspect, no facet, no moment of life that can't be improved with pizza.