The same way as Windows Vista, Windows 10 is going same way - lack of full working features, lags, irresponsibility, missing features or not working at all features and many other bad things are on the latest and finally RTM Windows 10 Builds. As you will see on my short Windows video review that describes everything, nothing much i cannot comment by now. :-)
Every reboot of the system, making it to start slower and slower, On this machine it took about 5 minutes to load to the Desktop and it's icons. Some of applications not work at all or one time working another no, for example including, these apps (Calendar, Mail, Movies & TV, Photos, Store, Weather etc...). One day Windows update just stopped working and showed a message "Downloading updates 0%" forever. Yeah, what Microsoft will say if they watched this video, - "THIS IS A HARDWARE FAULT". indeed...
Tested machine sysinfo:
Dell Inspiron 15 3000 Series
CPU: Intel Core i3-4030U 1.9GHz
RAM: 4GB 1666MHz
HDD: SATA III 500GB
Tested with Windows 10 build 10166