Windows 10 is free for 7 and 8 users. As well, a way it's better is the way the beta is. You can directly send feedback from within an included app, and others can vote and add their own opinions. It makes for better bug reporting and bug testing because more people use it and find all the kinks in the code.
Edit: So I noticed that there's one additional feature that's not noted yet because it's not a finished feature yet. You may have heard of the registry hack to enable the new login UI, which looks really nice, but if you're on a desktop or laptop, you may not have noticed this. My laptop can turn into a tablet, so on the side are some buttons for adjusting orientation and some different controls and whatnot. On the current login UI, you cannot use the orientation adjust button to change the orientation of the lockscreen, as it's locked for some reason until after you log in. However, the new UI allows you to adjust it on that screen, at a cost. It breaks when you go and rotate it, rendering your screen entirely black and will require you reboot to have it work again. However, since it's a registry hack to enable it, I don't think MS will count any bug issues on it since it's not a standardized feature as of yet.