Helpscout is our third help desk software service. While Helpscout resolves some of the issues we had with zendesk and desk.com, all three of them seem to follow the pattern of (1) make a small number of meaningful improvements over the incumbent software, then (2) stop improving thereafter. It's such a stagnant area of business software. Perhaps it's not sexy enough to encourage a sustained effort to innovate and improve.
We use Helpscout Beacon. It works great because it records information privately such as location, browser, etc. and open Helpscount cases if we are not available to respond right away.