Has anyone A/B tested the presence of the Olark widget on their site?

We're getting ready to roll out Olark on our site, but I'm kind of wondering if it will just increase the support workload without actually improving conversion rate much. When I was first checking out Olark, I'd pretty much decided to buy it, but because the widget was there (on olark.com), I spent some time chatting with one of the founders and asking questions. We'll probably start off with something like 20% of visitors getting the Olark widget.