That was their fuckup. It didn't need to be a worse mouse experience. Note that I'm not talking about metro here which is just a plain bad experience.
I'm talking about other small fine tuned details like the borders which are significantly larger, the larger hit area on icons, the introduction of the checkbox on explorer icons allowing multi-select without needing a keyboard. I'd mention the ribbon too but someone will lynch me for it.
In general none of these had a negative impact on the mouse, just a negative impact on the eyes as some people really hate the window border. Yet they were ultimately product breaking features if you used Windows on a convertible tablet.