To be totally honest, there are so many technologies out there that claim to solve analytics that it's tough to seriously consider all of them.

That said, we have looked at Druid, which is also a good example of using lambda architecture in practice (http://druid.io/docs/0.8.0/design/design.html -- note the historical vs realtime distinction). They use many of the same design principles as us, and one of our sub-systems is very similar to it. We still believe the pre-aggregation approach is critical for performance in our use case, though. Lastly, when we started building the architecture (mid-2014), Druid was very new, and I'm generally wary of designing everything around a new and potentially unstable piece of software.