A co-worker gave me some ribbing earlier this week because he saw me using my USB mouse in Excel, since I'm such a big proponent of using the keyboard.
Of course the keyboard rocks. The more you can use it, the better. But there's times in Excel (and much more so, in powerpoint) where using a pointing device is just more efficient. And the most efficient pointing device for excel & powerpoint is a mouse.
Most management consultants spend a majority of their time on the road where they do work with their laptops. Most don't bring a USB mouse with them due to the weight and the hassle. It's a mistake.
Quite simply, you can move a lot faster around on the computer with a mouse over the nipple or the TouchPad, regardless of computer. Adjusting PowerPoint slides, especially, requires fine-motor control to select individual objects. The mouse is far superior as an input device at accomplishing this tool than built-in pointing inputs.
Who cares of course, but this is the type of random thoughts you have when you're on the road 4 days a week.