Limited number of adjustments - the main difference between a task chair and a conference chair is that a conference chair shouldn't have to be adjusted 5 different ways every time someone sits in it. Usually conference chairs only offer one adjustment - a height adjustment that has become ubiquitous with office chairs.
Sleek profile - big, bulky chairs should best be avoided in the conference room to maximize the number of people who can take their place at the table.
Casters and lightweight base - provides ease of mobility. The fact is that in many offices, chairs rarely stay put for long.
Swivel seat - important for changing the direction you face with ease.