The input lag is one thing. What about the actual hardware? Remember the hockey puck? The pro mouse? The mighty mouse?
There is a joke somewhere in there... maybe about Jobs having to "invent" multi-touch because he couldn't grock the concept of a mouse.
In particular, the multi-touch trackpads are the meow part of the cat.
Recently I've had to use a Windows laptop (Lenovo) for work and I've yet to find a suitable external mouse - the track (pad|point) on the laptop is over-responsive, and both Microsoft and Logitech drivers are buggy in their application.
Finally (and this is only on my recent laptop) the external mouse and keyboard take ages to "wake up" - and they're USB (the bluetooth ones sometimes require me to go to device properties in order to become visible)! On my Mac, external inputs respond immediately once plugged in, and even bluetooth is almost seamless.