I don´t know about comparisions with other routes, but planes are still flying from Madrid to Barcelona. Note that most connections are made in Madrid, and these feeder routes are still essential. The point is that train from both cities takes the same amount of time. If you get an offer and go from downtown to downtown it could be convinient. If you don´t get an offer, plane is more convient and usually cheaper.

About 50 flights a day in each direction. Served by Iberia, Spanair, Air Europa and Vueling. Competence will be fierce now.