Whether you complain on the spot or via email (I strongly advocate the latter), expletives should always be avoided. Swearing is indulged in by witless whingers whose brawn tends to far outstrip the capacity of their brains.
It is quite wrong to assume that an employee of Marks & Spencer or Dixons will respond better just because the account of your grievance has been embroidered with colourful references to human anatomy. A stream of invective will generally produce the very opposite of a positive reply. The cunning complainer prefers to express his or her complaint by using plain and essentially polite language.