For me, Win 7 was a compelling upgrade from XP because it seemed much more polished and refined. I liked the huge improvements in tools like Windows Explorer as well as the included backup and imaging tools and additional security. Some of the features of Aero were very useful such as Aero Snap. Overall, I thought Win 7 was a better OS than XP. I actually, upgraded all of my XP machines to Win 7 because I liked it so much.
There are things to like in Win 8, it boots and shuts down quicker and is more secure (more secure than Win 7, FAR MORE secure than XP). I like those things but not enough to upgrade a working Win 7 machine to Win 8.