It is of critical importance, since it shows your ability to express yourself well, using clear and precise terms. It also allows you to stand out from the crowd.
Things to avoid (you would be surprised to see what we receive)
grammatical and typographical errors
mistakes in the name of the firm or the recipient
handwritten letters
The C.V.
Always remember that the person who reads your c.v. will probably be reading 150 others. What makes yours different?
Fancy paper and binding are much less important than the content of your c.v.
It must neither be too long nor too short. It must include enough information on all your accomplishments to keep the reader interested, without being the size of a book.
You must include your transcript. If not, you may be rejected automatically. Very good marks almost guarantee that you will be interviewed.
Your marks might be better? Be careful with the explanation you provide.