Not much. Probably just support for some hardware that needs drivers like my 3d printer. But that’s what Vans are for right. Most other “windows only” apps work fine under WINE. If I have to say one thing: powertoys (some of them)

My thinkpad’s battery is much happier on Linux than windows. It’s hibernate and sleep work as expected. My windows work laptop can’t even wake from sleep properly unless I I open the lid and re plug the dock each time it’s gone to sleep.