Gnomeo and Juliet is absolutely amazing. It is fairly faithful to the Bard's plot, with the exception of a positive, chipper, happy ending. At which point, if you are like me, you start scratching your head and thinking "now how does that work?".
I won't spoil the plot, but I can tell you that it is a really clever little interpretation of the play. It's simple enough for children to understand, with the pure, sweet kind of animation they enjoy, with some sly jokes slipped in for the adults to enjoy (for example, Rosencratz and Guildenstern movers? Hilarious!).
Yes, the die hard Bard fans are probably a bit upset by the film...but if you can enjoy things like "The Complete Works of Shakespeare Abridged" you can enjoy Gnomeo and Juliet. Re-imagining fair Verona in terms of garden gnomes is extremely amusing.