Compared to Twilio, Tropo has an <i>awful</i> API. Also, a few features Tropo publicizes (esp. to do with IM) just don't work - you end up going to another Voxeo company to get semi-working functionality (IMified), but then some of <i>that</i> IM functionality doesn't work either, and IMified support is non-existant.<p>Personally, I hope that Twilio goes all-in on the "communications" part of "cloud communications". I'd gladly pay for working and supported IM endpoints with a sane API.