Using a specialist recruitment agency can save you time and will provide you with exposure to a greater range of opportunities because they have expert sector knowledge and experience. In addition, they have existing client relationships and may be able to introduce opportunities which you may not otherwise hear about.
Following any interview - be it positive or negative call your consultant and exchange feedback. Good agencies continually strive to improve their service. If you have any feedback or suggestions about any aspect of the service you received, notify the agency directly either via your consultant or through a customer satisfaction survey.