Your business stationery can shout “we are a forward thinking company”, or it can state “we are traditional, solid and reliable”, or any one of a million alternatives! It is not just a piece of paper with your address on it.
So few companies consider the implications of their letterhead design. Colours used, font, layout and even size all make a statement that will help your audience form an opinion about you.
A non-standard sheet size on an exotic stock with vivid colours will produce a very different impression with your audience than a traditional sheet size on standard stock. Both have equal merit in appropriate situations, but working out what you hope to achieve with your design is critical.