Unless you go for Enterprise you can only have a single worker per site making QA and staging hell.

Their JavaScript environment/APIs are not standard and there’s no proper spec that I could find.

The debugging environment/IDE is decent for an in-browser one but we had some horrible issues with a stale version being loaded from local storage and accidentally applied to the entire site effectively bringing us down for several minutes.

On every change I also saw several error pages myself during warmup period which made me wonder how many customers were getting them.

This was all ~6 months ago though so things might have improved since then.

Performance wise we’re very happy with it though as it beats the Apache reverse proxy it replaces hands down.