yeah, twilio seems pretty cool, and i'm looking at it for another voice/political project. but it's basically an api for level 3 with some nifty features tacked on, so for a project as voice-heavy as a predictive dialer that doesn't need the extra features, i'm guessing it makes more sense to find a developer with voice experience and avoid the markup and the added layer of potential problems. if somebody with twilio or other voice experience is listening, i'd love to get another opinion.
This may violate their AUP
"Using the Services in connection with any unsolicited or harassing messages (commercial or otherwise) including but not limited to unsolicited or unwanted phone calls SMS or text messages, voice mail, or faxes."
http://www.twilio.com/legal/aup
That said, I'll definitely consider them in the future.