We evaluated InfluxDB for our TSDB solution and found it to be generally high performance (up to about 100k unique series). Kapacitor also had some promising features for realtime aggregations, but was ultimately pretty buggy and didn't have support for out-of-order event processing. All in all, it looks like a great suite of products and we're curious to see how it evolves over the next few years.
Like many other users here, we were disappointed about paid clustering, but when the original press release said $400, we were willing to wait it out and see. However, we ultimately decided to go a different direction after seeing they wanted $20k+ to run clustering on a 256GB node. We ingest 10s of millions of data points per day from IoT sensors, and expect our data size to far exceed that capacity.
That said, we plan to run our own Cassandra cluster w/ KairosDB (http://kairosdb.github.io/) acting as a read / write abstraction layer. It'll cost us about $11k to run the cluster for the year, with 3 nodes @300GB/ea., leveraging Cassandra's (free) and open source clustering, HA, and replication technology.