RyGuy hits it in the head. The show has been designed for young audiences and their families, not the standard die hard Disney fan (though as one myself, I can't get enough of it).
Of course, I disagree with the comments made before, but it is a matter of personal preference. I disagree that Sofia and the rest of the characters are bland and lack personality. Yeah, the characters are a bit dumbed down from the typical cartoon show because this is a preschool show after all. But they still manage to be fun and lovely. Sofia is just adorable, and she feels very natural in her role. She acts and sounds a lot like a child would, and it is her interactions with the other characters that make the show so enjoyable.
I LOVED it when Sofia gave Cedric a gold star after he helped her out. That was so sweet of her. That's the other thing about the show: Sofia is such a great role model, perhaps moreso than her older Disney Princess kind. I like that she doesn't let gender roles define who she is, much less her princess status. She makes mistakes but tries to make up for them and is even willing to take the fall for her siblings if it means they can be happy. I like how that element was handled in the show, that a lie is still a lie, even if it was done with good intentions.
One of the reasons I loved the Slumber Party and Trolls episodes were their morals. In Slumber Party it is about being yourself, while Trolls was about hearing the other side of the story before creating a conclusion. Considering how much people are giving up individuality to fit in these days and are quick to jump to conclusions, that's a great thing for families to see and learn.
The other characters are just as fun. I admit James is kind of meh, but he has a lot of fun moments (like his whole fanboy-gasm over the circus on the last episode). Amber is a fantastic character, being able to be haughty without being too over the top that she is unlikable. She has a lot of funny moments, like when she tried to keep the king and queen away from the broken picture. Speaking of which, the king is also fun, and even the queen gets some fun lines (like "I say it to the kids all the time!"). And lest we forget Cedric, a villain so campy and so over the top he is gaining his own fanbase. And I like that the show doesn't go out of its way to treat him like a huge villain (a la Crocker on Fairly Oddparents), and they give him a break and even a chance to redeem himself.
The songs are GREAT. That stunned me when I first saw the episodes as usually, I feel the songs on these shows are so mind numming, repetitive and obnoxious it scares people away. Yet, Sofia manages to have really fun songs a la Disney's animated classics. They are quite catchy without being overbearing and serve a purpose in the story.
As for the animation, not gonna lie, I feel most people are putting it down because they have a huge bias against CG animation. Sofia the First is far from THE best looking CG show ever, but it is pretty good, especially when you compare it to the likes of the new TMNT series as well as the Kung Fu Panda series (though Dragons is really nice looking). Plus, the show proves that we have come a long way since the early to mid 90s when CG was a novelty and we got the worst.
Dare we forget that these were considering breakthroughs...
(not saying the show is bad, it was awesome, but pretty low on the CG quality spectrum).
Sofia the First succeeds in that it doesn't try to be super realistic, nor too stylized. It establishes a balance between the two, so the look is very pleasing. The only issue I have with it is that at times the character design doesn't always seem to work well with 3D, such as some of the trolls on some angles, and especially James. But considering this is budget, TV CG animation it looks great. Compare it to the Octonauts and Doc McStuffins and the show is a looker.
But I can see how it isn't everyone's cup of tea, it is a show designed for an audience in mind. Yet, I think it transcends a lot of ideas as to what pre-K shows can be. Heck, it goes beyond what a standard "franchise" show is and entertains while teaching lessons. I definitely approve of Sofia, which surprises me since I came in expecting nothing out of it.
Sure. Because anyone who would criticize the animation of a CG product must have a "huge bias" against CG. 
That's never been done in a preschool show before! 