The most important feature to me is that we can connect all our systems together in real time without having any manual errors or issues! It's very user friendly as well so it has helped us immensely over its short period of use for many years now!! There are no downsides at this point but I guess if you're looking into migrating from other providers then there will be some problems because they don't have much experience using matillion yet (just started working 2 weeks ago).
But overall everything seems pretty good about their service. We've been able to get data from several different applications/databases connected up easily.