I upgraded an old Windows 7 lappy and I must say: first impression isn't bad at all.
On an other lappy I have Windows 8.1 (which, after manipulating it a bit and using 'Classic Menu' to have a normal start menu) isn't bad either. In fact from a user point of view, it's quite similar to good old Windows 7. So I'm not sure if it's worthwhile to upgrade to 10 at all.