Faster booting to a truly usable desktop rather than 1 minute to get a non-functional screen then another minute for enough of the OS to be brought up to do anything.
Page compression for low memory PC's is nice to have too.
Boot time is a non-issue if your boot partition is on an SSD, which is the case for most serious users today.
I actually measured the difference. My Windows 7 used to boot in ~20-22 seconds. With Windows 10 it went down to ~15-17 seconds. Sure, Windows 7 was a bit slower. However, it also didn't have forced reboots like Windows 10 does, which in my eyes more than makes up for it.
Page compression for low memory PC's is nice to have too.