Outbound calls to a Chinese number had a failure rate of about 50% (failed with a couple of different error messages, can't quite remember what exactly they were anymore, although I remember thinking they didn't seem particularly relevant... like claiming the number dialed was busy even when it definitely wasn't, etc). Also sometimes the calls would go through but then disconnect immediately after I picked up and I would get billed for them. Basically, my experience calling China was that the service was totally unreliable and a bit expensive (by expensive I mean I was unhappy being billed for dropped calls).
Thanks, there are different challenges with international routing by country and by receiving carrier. I'll definitely pass this information along, and if you have specific calls (I'd need your Twilio account ID to look at them, better sent via email) that will help a lot, too. We know international support is important to developers everywhere, and we're definitely working on it.
International is hard. I know from experience. That's where Tropo has one clear advantage over Twilio. Tropo is built on the Voxeo network, which has ten years of international experience, is deployed world-wide (seven data centers), and integrates directly with most of the carriers around the world.
I believe Twilio integrates directly with a single carrier (Level3). Last I checked they use/resell bandwidth.com for most of their calls.
To correct a misconception, Twilio works with a variety of carriers, including Level3 and Bandwidth.com. Much like Google Voice, we work with a plurality of vendors for redundancy, geographic coverage, etc..
Voxeo also works with Bandwidth.com. "Bandwidth.com shares Voxeo's 'All-IP' worldview and as a result is an important voice network partner for us." --Jonathan Taylor, Voxeo CEO
