At work (consulting/development shop), we went far down this path a few years ago. Conclusions:

1. CQRS+ES works great, if you implement it carefully, which requires discipline. We ended up creating our own framework (ugh) to make it easy to go down the right path.

2. There are trade-offs, of course.

3. You are only one smart agile thinker-in-a-pinch away from stepping away from the discipline and creating really tricky complexity and far more negative trade-offs.

4. There is very little market demand for this approach among the typical enterprise business solutions we work on; though as I understand there are some sharp peaks in certain areas of financial services.

(The odd thing is... we have financial service customers, just not in the particular domains where there is demand for CQRS.)