The features are very customizable, can be used as an API for third-party providers or use it in your own applications with ease of configuration options - you just need to know how! We're using speedments web client mainly but have also done some integrations into our app engine backend too (which is awesome!).
There aren't specific problems that we see at this moment though I would say one thing about performance could definitely improve more especially since there isn’t much customization yet when compared between other cloud service like AWS Lambda etc., But overall its been smooth sailing so far considering all factors from cost/benefit perspective.