Test group’s first impressions rather than asking for a long evaluation

In his book Blink: The Power of Thinking Without Thinking, Malcolm Gladwell suggests that formal marketing research, including focus groups, is not very valuable and effective because the people being asked to evaluate the product do not take enough time to thoroughly evaluate the product. As a result, it is more effective to just to ask the test group’s first impressions rather than asking for a long evaluation. What are your thoughts on this matter?