Just a quick one, I've started to use calculated fields more and more and came across a new restriction the other day.
Problem
You can't reference a lookup field type in concatenation. You will get a error "You can't set the value country, which is of type lookup, to type string." Shame I would have thought Dynamics would have been able to handle this by now.
Solution
The solution for me, was luckily I had a workflow that was firing on create already so I just popped a statement into it to write the lookup value out to a new text field. Then tweeked the calculated field.