So I finally got a reply from Delta, after over a month. Here's their bogus claim, denying compensation:
"I certainly understand the inconvenience caused to you and your family when Delta Flight 49 on January 5, 2015 from Amsterdam was delayed due to mechanical reason. The delay constitutes “extraordinary circumstances”. We took all the reasonable measures we could under the circumstances and made every effort to offer you care and assistance. Regulation (EC) 261/2004 does not require compensation in this event. "
Sent me a $75 voucher. So now need to pursue this case through EC, I guess?