we just got started using it at my company (serpIQ.com). We're tracking a SaaS signup funnel though, so we're only collecting a few hundred data points a day. It was tricky to get setup, but I would imagine we're an ideal use case for them.

Also, they offer a deal where if you put a banner of theirs on your home page you get like 150k free data points a month extra. Definitely sweetened the deal for us.