What would be a critical appreciation of "To a Skylark" by Percy Bysshe Shelley?

Before tackling this question, it helps to understand what a critical appreciation is. A critical appreciation is a knowledgeable evaluation of a piece of literature or poetry. For instance, the reader must have enough relevant knowledge about the particular piece in order to construct an informed opinion about it. It's worth noting that a critical appreciation can like or dislike the piece of literature being examined; the important thing is to know enough about the work to give good reasons for why you like or dislike it. 

With this knowledge in mind, let's look at "To a Skylark" by Percy Bysshe Shelley. Your critical appreciation will depend on the particular context from which you approach the poem, and also on what you like or dislike about it. It's still possible to provide some examples, though. For instance, you could say you like the poem because it skillfully uses a skylark as a metaphorical representation of the natural world. Conversely, you could say you dislike the poem because its archaic language makes it difficult to read and comprehend. Whatever the case, you'll need to back up your particular opinion by offering a careful and insightful analysis of the poetic characteristic you're discussing. Your opinion does not necessarily matter, as long as you back it up with a sound evaluation of the work in question.