The thing I don't like about analytics as a service is that, most of the time, it's highly opinionated about how to track and visualize data. We tried a number of analytic services in the past, but no matter how flexible they were, we always found corner cases or certain ways of visualizing and presenting the data that we wished existed but for some or other reason weren't possible, because each respective service always expects you to do things in a certain way at the end of the day. Which is understandable, because you can't have a fully featured dashboard right off the bat without an opinion about how should that work and be presented, so as an analytics provider it isn't an easy problem to solve unless you go the keen.io route and offer an analytics as back-end service only.

I guess what I'm trying to say is that, while services like these are great, I find that eventually after a certain size startups will almost always need to have in-house analytics infrastructure to cover all use cases and needs specific to the business. Not that services like Amplitude don't have their place, which they do, I just wish there was an universal solution to that problem. But I suppose you can't help rolling your own infrastructure given specific enough needs.