Yep, our planners have a computerised system that looks (amongst other things) at a three dimensional wind/temperature matrix and compares various routes and altitude profiles between the departure and destination airport. We eventually get presented with a flight plan planned along the most efficient route at the most efficient flight levels. There's also a printout of a simplified matrix in our flight deck paperwork and these enroute winds and temperatures are loaded into our onboard management computers so they are able to run the enroute fuel and time predictions .
As welliewanger has said, it's a big deal for the all airlines because of fuel costs.