I love how you can target and schedule notifications and in-app messages to be as specific as you want. The intelligent delivery option is also beneficial, getting it to the recipient at the best time they'll engage with it. Geo-targeting your message is also useful. We can create campaigns based on where our members are. With a bit of creativity, we can drive them to our property with these messages.
I also have to mention that the team behind Kumulos is also fantastic. They have great support, are fast to answer your questions, and also listen to you. They take into account your input on the product. I've seen changes they done because of my team's feedback. Review collected by and hosted on G2.com.
The thing that sticks out the most for me would be the user interface. While the design may be on the modern side, it isn't very intuitive. It takes a while to figure it out on your own, or you'll have to get a few pointers from the support team. Thankfully, that team is excellent.
There's also no way, at least not that I know of, to resend the same message without having to redo the whole setup. We send multiple tests out to different stakeholders before the final message. Though there's a button for test users, that only goes out to one team. If there are other stakeholders, we have to recreate the message.
There are other small things, like the rudimentary user role settings, strange per message analytics, etc.; but they really aren't deal breakers. Review collected by and hosted on G2.com.