It's also just like using the resolution scale in game from 100 to lower. But the main difference is DLSS does it on the fly based on demand from the GPU.
Having not seen it in action my concern is a noticeable change in quality, like when you're watching a stream and the bitrate changes. If everything suddenly looks slightly more blurry (because it's upscaled 1080p, not 1440p) then back to sharp a few seconds later it could be really annoying.