Apple is one of the only companies that does the trackpad placement "right" - it's centered on the case, but also not far off center with the "B"
It's also place a decent distance from the keyboard that there should be no reason to be hitting it by accident with your thumbs, even though it's larger than many pads found on commodity machines. You've also got to love the fact it's sunk only about .5mm from the top surface of the case (my GF's Toshiba Tecra collects all kinds of crap because it's like a 3mm deep dish).
Mark, keyboard placement is often times poor as well. Some machines have the main keys way off to the lef. It's understandable when mimicking a destop keyboard, but keyboards for notbooks need to be designed to work around these issues (because you obviously can't move them like you would with a desktop model).
I used to hate trackpads, but as Matthew noted, after you start using one, you'll get better and better and realize that those sticks/points are not a good substitute. When I sit down at my desk to do work though I use a Microsoft Laser 6000 Notebook mouse.
Machines with both a stick/point and trackpad are the worst of all because they crowd the bottom half of the case with a bunch of extra buttons. I find ONE button below the trackpad to be perfect. On the Mac I click normally for a Left click and I touch two fingers on the pad while clicking for a Right click. This is MUCH faster and ergonomically pleasing than trying to press a second button somewhere off to the right.
Bruno