I'm being pretty generous with the two stars. Overall, it was a disappointment. Their sales pitch and onboarding were very good (hence the two stars) but things went downhill fast. Here were the two big issues:

1. Their UI lets you configure a lot of useful things, but if you are not on their top-level plan, it's not possible to get access critical parts of the data! So, you set everything up thinking that you'll get some valuable results, but then you're expected to go premium to access it. Bait and switch!
2. I wanted to set up A/B testing around an event that was centered on an HTTP POST. No luck. I couldn't get anywhere with support and ultimately they told me, "Sorry, it doesn't work this way." Unfortunately, that workflow was my most critical. I got frustrated and stopped using it. I've been advising other companies to stay away after this experience.