The ease of use, how well it integrates with our own system & API's we have built for clients - even if they are not using us as an intermediary! Would like to see some more features added or developed in terms that don't cost extra money (like custom fields).
We've been able solve all kinds problems integrating data from different sources into one place so everyone can get their arms around what has happened when something goes wrong at least once per month due only because someone didn’t understand why things weren'...