I like that it's easy to use, you can add your own domains or IP addresses as well which helps with testing for deliverability in general so we don't have to rely solely off of google analytics data alone when looking at our senders scores (which are often not reliable). It does take some time getting used too but once its set up correctly there isn’t much else needed from my side unless i'm doing something manually via excel/power query etc - where they do offer an API if need be though currently only support csv files however this could change soon! We're using them mainly internally primarily targeting US companies / customers within their country unfortunately haven't been able to target non-US markets yet due to restrictions placed by Google Adwords api rules regarding sending bulk emails outside these countries.