I kind of hate the way they handle write calls, they tell you to just try it and if it fails with a readonly error your app has to respond with a specific header that lets fly redirect the whole request to the main region.
On one hand it's fairly trivial, on the other it adds quite a bit of latency and now you need to customize your application code to the service(s) you're using, breaking portability.
Since in their pg stack already includes proxies, I'd love for them to have the proxy simply redirect write queries to the correct location instead.