Before we got a tool, there was no reliable way to measure audience size. We had do things like count the number of re-tweets manually. We had no way to track impressions, or mentions or to track how many people clicked a link. Sprout allowed us to track everything and save an enormous amount of time.
Bazaarvoice has 3 Twitter accounts, and 1 Facebook account. Sporut Social is used to track a wide range of metrics in Sprout to ensure that marketing strategy is successful:
Audience size (# of Twitter followers / conversation rate)
Number of Twitter mentions of BV
Facebook impressions (# of times a follower sees a BV post)
Amplification rate (Twitter re-tweets)
Applause (FB likes and shares).
We do not use Sprout to measure blog shares or viral lift (# of times our content is shared to a social network compared to # of times content is clicked). Sprout cannot track this, so we use AddThis to track these metrics.
Also do not use Sprout for publishing (automated posting to FB and Twitter) because I prefer the Hootsuite publishing user interface. I had used Hootsuite for publishing in the past and really like how easy it is to use. Looks a little better than Sprout.