It's good. In fact, to a large part it's very good, although there are some weaknesses.
First of all, it takes a while before it starts getting interesting; it takes too long setting up the story. This could have been fixed by having better songs for the first couple of musical numbers featuring first Rapunzel and then Rapunzel and her evil "mother" – or somewhat stronger performances of them.
These are very much Alan Menken songs – when I heard them I thought immediately of Beauty and the Beast but had to wait until the credits to have it confirmed that it was indeed Menken who'd written the score – so they're of course competent, but Rapunzel's song about her longings is very much the sort of song you'd see in any musical, and it's unfortunately rather bland, without any special hooks to catch the listener. Unless it's sung by a very special voice, it becomes mainly exposition – the images accompanying it are good, but not strong enough to carry the number by themselves.
The number where the evil "mom" Gothel undermines poor Rapunzel by telling her how weak she is and how evil the world is is better, but I sat there wishing for more of a Scar quality to Gothel's performance – I think some controlled over-the-top evil à la Jeremy Irons would have made this song strong enough to stand on its own, instead of just being another musical number.
But then come the strengths. The story is strong and complex; the Disney story men have really done their job on this one. There is drama, and plenty of it, with several conflicts going on at once – unlike the horrible overlong TV special Chicken Little, this really is worthy of a feature film and capable gripping and moving the viewer. There are strong characters, great sight gags, a clever plot device to symbolize Rapunzel's longings that carries the film forward and adds emotional poignancy to it, and an intelligent way for her to discover who she really is without resorting to simplistic tricks or deus ex machina. And the animation is just gorgeous.
Textures, body language and movement, slapstick gags, 3-D – they're all marvelous. The film simply looks great (well, except for the character designer making the women's eyes way too large, unbalancing their faces; that failed). Best of all is... the horse.
Maximus is the horse of the captain of the king's guard, and he's determined to catch the thief he starts the film hunting – Flynn Rider, the movie's hero. Maximus has a fantastic range of expressions, and he goes through them at a rapid-but-not-too-rapid clip that is a joy to behold. Whoever animated him did an outstanding job, and although he isn't one of the lead characters, he takes away any scene that he's in – almost like Thumper.
Considering that I've even seen some idiotic faux-"feminist" complaint that Mulan was anti-woman – because of the law that made it a crime for a woman to join the army, and because Mulan's soldier training made her strong (to quote the great Dave Barry: I am not making this up) – I expect there will somewhere be somebody who'll claim that Tangled is anti-woman because Gothel is an evil controlling mother. Don't listen to that person, or anybody else who's trying to convince you that you shouldn't watch this wonderful film, because they are not your friends.
This may be computer animation and 3-D instead of classical animation, but it's nevertheless classical Disney. Recommended.