Ah, great. Seems I can share the frustration with others. I've been using win10 for a week now (new laptop) and was using win7 before for 8+ years. Never had a problem with the mouse or the keyboard, but since win10 typing has become a niiiiiiiiiightma !
No, it's not my spelling. Some letters are just randomly not handled and some are autoooooorepeated after a short lag. Similar things with the mouse, which once in a while (say once or twice everyyyyy 10-30sec) freezes for a half-second or so before moving on.
I tried different USB ports, different mice & keyboards, all the same.
Highly frustrated, as typing is 90% of may daily work.