Originally Posted by ashill

The bolded part is not correct; car seats and strollers are certainly acceptable as checked baggage, and bag fees don't apply. I have checked car seats at the ticket counter multiple times on many airlines, including Delta.

Everything else you say is correct. If I'm checking bags anyway, I'll usually ask if there's any chance of an open seat in our row. If there is, I take the car seat to the gate (often having luck getting the open seat, and gate checking if no seat is available at boarding time). If not, I check the car seat at the ticket counter. If we're otherwise traveling carry-on only, I take the car seat to the gate either way.

This can also be found here; it's the first hit in a Google search for "delta check car seat".