I've used it, in production for almost 2 years now. In the interest of full disclosure, I also did a case study for them. What I can tell you is that the product does exactly what they advertise. It does point in time recovery (our recovery point is currently about 7 seconds for our db servers), and it is almost brainlessly simple to set up. We evaluated the product against VMWare SRM, and it proved to be a better solution from top to bottom. The failover testing is probably the best implementation I've seen.

For virtualized SQL servers, the product does a fantastic job. Replication does tend to work best through a bandwidth optimizer like Riverbed, SilverPeak, etc.

There are a few downsides - agent vm's required on each host being the main one - but overall, my experiences have been really positive. YMMV, but I'd definitely recommend doing a POC with them if you want to test it out. Compare it against SRM, and see how it works for your environment.