@Mike: There are a whole bunch of use cases. I'm surprised to learn about new customers using Rx in different ways every week. Most recently:
- Data center monitoring scenarios - e.g. computing moving aggregates of CPU utilization, noticing peaks, etc.
- Sensor and signal processing systems - e.g. collecting and processing data in smart grids, network centers, etc.
- Robotics where queries over sensor inputs control servos etc. - e.g. we've seen queries being compiled into embedded code.
- GPS processing systems to tame events of long/lat pairs - e.g. filter out noise, correlate with other data stores, etc.
- Intrusion detection systems by processing historical logs and real-time data - e.g. logs of requests / IP address, try to find suspicious outliers.
- Blending UI events with asynchronous requests to web services etc. - e.g. take input in a text box and launch async web calls for completion etc.
Stay tuned and you'll see us "eat our own dogfood" in various places. Quite a few products today are shipping "powered by Rx" (most lately PowerView in SQL Server 2012, various online services in Bing, but also yet-unannounced projects), and the number is growing fast.
With regards to debuggability, we've done a lot of work in this release to make callstacks readable, approachable, and understandable (see the blog post). This is just the end of the beginning of work we're doing in this field. So again, stay tuned!