Loved using Mixpanel for an iOS app last year. We’re in the process of connecting Mixpanel to a web-based HR dashboard tool via Segment. Our first choice was Kissmetrics, but their pricing isn’t very attractive to a seed-stage startup.
Because these bought-not-built tools keep changing and new ones keep popping up, it’s a good(IMO) idea to have an in-between like Segment or Google Tag Manager.
Having stumbled through a homebrew solution using an unholy marriage of Google Tag Manager, Firebase, Heroku, GA, and too many Excel formulas, I do recommend paying for a tool that does it right. So long as it does what you need. And if not, it’s in their best interest to find a solution to your analytics challenge.