A friend of mine is a professional photographer, he is using his trackpad to process and edit his pictures. Hundreds of them per session. And it's not like he can't afford a mouse or even specialized hardware.

And having tried Apple touchpads, they are actually good, so much that they released a standalone version for desktop computers. On every PC I have tried, at best, they provide you with a pointing device in case using a mouse is impractical. I don't intend to buy a Mac for several reason but I have to admit that their trackpads are not in the same league.