Great article. There are just a few things that I would add to it.
1. The metrics comment could not be more true. You cannot think hard enough about the actual problems you will encounter and what metrics you will have. Have a common way to pull information about each service, and to analyze it in some common place.
2. Standardize, standardize, standardize. When someone is answering a page at 2 AM and has to deal with a component of your system that they don't really know, the more it resembles other components, the better. Think hard about how you can get every service to be written in such a way that the same critical information is available. Where is it documented? Who do I page? Where is the monitoring? Yes, random third party components won't follow your standards, and will be hard to integrate. But standardization is a good thing.
3. You need to be able to send canary requests through that trace through your whole infrastructure. You should be able to flag a front end request, and have every single request that it generates through your entire system be logged somewhere so that you can see a breakdown of what happened. Hide this so that nobody can use it to take your site down, but build the capacity for yourself. (Standardization will make such a system much easier to build!)
4. Randomly canary a small fraction of your traffic. There is tremendous value in having a random sample of traced traffic. When you're trying to understand how things work, there is nothing like taking an actual request going through a complex system, and seeing what it did. Furthermore if you've got intermittent problems for a small fraction of users, being able to look at a random slow request really, really, really helps you track down issues that otherwise would be virtually impossible to replicate.