I e-filed my federal return the first week in March. The Where's My Refund site says it's still processing.
But I know there's a complication. About 3 weeks after filing, I got an amended 1099 statement from my brokerage firm. It documented additional dividends and capital gains earned on one of my accounts. Of which I was unaware and obviously did not report. So in April I filed a 1040-X amended return. Which had to be sent by mail. (Apparently, only tax professionals have the software to e-file amended returns.) It wasn't as bad as it could have been. I'm still due a refund, but reduced by several hundred dollars.