I see a lot of people picking on Apple's mice, but I wonder if those have used the Magic Mouse?
I have both the Magic Trackpad and Magic Mouse. As much as I want to love the trackpad, I find myself loving the Magic Mouse so much. I think the Magic Mouse I the best Apple mouse ever by far and may be the best mouse ever. I think people complain about how short it is but that is what allows one to scroll by using it partially like a trackpad and partially like an old school mouse. It takes some getting used to, but it's hard to let go.
I only use the Magic Mouse & Trackpad when at my desk and attached to ACD, but I feel so much more productive with it especially versus the trackpad when using both 27" ACD and native display.
I wouldn't recommend using a mouse away from a desk, as the MBA's trackpad is great when on the go. If I didn't use an ACD, I don't think I would ever use an external input device. When at desk, I am using ACD, Magic Mouse, Magic Trackpad, and Apple wireless keyboard. The system is amazingly well designed when used together. Apple's products definitely all work best when paired together.
I definitely don't think most benefit from thinking Apple has made the same mistakes with Magic Mouse as it did Mighty Mouse. The Magic Mouse works amazingly where Mighty Mouse failed with scrolling and cheap feeling design. People just need to give it a week or two then it feels terrible going back to anything else.