If you are already ticketed (e tickets or paper tickets in hand) and have no changes, then curbside check-in can be much faster than standing in line at the ticket counter.
the disadvatage- I have heard that if your luggage is lost then the airlines will fight with you over responsibility since an official airlines employee did not check it in.
That said, I used it the first time last week to avoid a 30-45 minute wait in line with absolutely no problems.