I like that they have 24/7 access to my data - no matter where in North America or around world i am! They are very responsive when it comes time implementing new features into our system as well as helping with any issues we may be having at anytime during business hours (even weekends).
Not much really but if you're looking out of an application integration tool then this is what your after. Honestly haven't had too many problems using them so far though there's always something going wrong somewhere haha :P But overall their service has been great thusfar!!