As a customer, adding live chat benefits me personally a lot. A quick easy way to ask a question. I usually test the live chat before purchasing to ensure the quality of the support team, response times etc. Sometimes live chat can be a life saver in an emergency (server down etc).
As a host, it has increased my conversion rate highly. After being able to answer pre-sales questions, I noticed conversion rates going up a lot. People tend to just click off if they can't have their question answered instantly.