They have been very responsive (email support in particular) when we've had questions about our product's ability or inability to integrate with other services such as Zapier. Their price may appear high relative to competitors but they're offering quite good value compared to any full featured alternatives I'm aware of out there at this point. Definitely consider their pricing structure if you were looking more towards just an email marketing solution without really needing much else with regards to integrations etc. We don't do anything particularly special here beyond being able to send emails, so it works well enough that nothing has come up yet.