userfly: Instant web-based usability testing service

Userfly is a new web-based usability testing service that looks pretty exciting. When you set up a new test on the service, you're given JavaScript to enter into your site template. Userfly captures sessions including link clicks and time spent on the page, and records screen events including mouse movement and keystrokes.

This looks like a pretty nice service for certain types of observation. There doesn't appear to be any options for interacting with users, e.g. video/audio capture, task marking. I suppose on a siloed test server you could drive test session tasks and do an additional recording via other software. But at that point, you might as well go a more traditional route using web-based methods. But this should definitely be useful for some testing needs. Would love to hear more about people's experiences with this.