Hugely responsive customer support team. Very easy to chat with and helpful with answers. It's easy to upload lists, and they offer an email verification service that checks for invalid addresses on upload.
Honestly, there's almost nothing to like. The UI is challenging, the system behaves unexpectedly (eg. you think a campaign is paused or archived but it keeps sending emails), you can't schedule multiple campaigns in advance because one contact can't exist in multiple campaigns, there's a limit of 400 emails sent per day (which is usually fine but can be frustrating in certain circumstances), there's no unsubscribe option/link, there's no clear indication who has received a campaign once the last email has been sent, it doesn't show you lists of who bounced, responded, clicked. It's really only in its early stages. There are numerous typos throughout the application making it feel unpolished and not market ready.