I've used earthchannel for several years now, first as an attendee at live programing then later in hosting my own event with them! They are always professional but flexible enough to work within our needs when it comes time for re-brandings or even just simple changes needed during service delivery period (for example adding new features).
Nothing so far really - they have been very good partners over all these year we worked together. We had issues here & there which i'm hoping was due moreto us than their product itself though nothing major thusfar :) As mentioned above; great partnership overall!!