It's actually an awesome feature that will probably get more attention once it's gone retail and reviewers are benchmarking the game.
Say you run the game at 1920x1080p, you can run the game at 2880x1620 internally and it will output to your monitor at 1080p delivering a much better image and negating the need for running MSAA/post-AA. It's super-sampling and will deliver the most amazing IQ you can get in game.
It will likely be a reasonable feature to run for gamers playing at 1080p and using say, two AMD R9 290X cards or two GTX 780s etc.