We built our entire sales inquiry, customer support, and help system around intercom.io. It cost $50/mo for the first year (their startup introductory plan) but we never would have gotten off the ground without it. At launch our product was pretty raw and the documentation was thin; we got through that period by being constantly on top of customer support.

Customers are incredibly forgiving when they feel that they're being listened to. This kind of support is one of those "things that don't scale" that you can do in the early stage to build a foothold while you refine your product.