Just putting the feelers out to see if anyone uses a media management company?

I've got a meeting next week with an agency that will look after all my 9 Websites (not inc hosting), doing any updates needed on said sites, manage the social media with targeted campaigns through social media and mailchimp etc.

Also inc is a a new website for Derbyshire Wedding DJ which has sadly fallen behind on style and more importantly traffic, a marketing review of the business as a whole with going forward strategy.

All the above is done by a monthly retainer fee.

Anyone have any experience with agencies and can offer any pointers, advice etc?