You need to strike a balance between both. Too much professionalism and your customers will be annoyed. As will be your boss and your colleagues. It means you will make professionalism and end in itself and forget about getting things done. Too big a focus on getting things done will make you cut corners. Write bad code. Being not professional.
by Stephan Schmidt
A great article. Really.
http://codemonkeyism.com/developers/
