I use my laptop as a primary computer, and have become quite accustomed to using a trackpad full-time. It's become a bit of a necessity, as I don't feel like carrying a mouse with me. Newer offerings such as the Go Nano from Verbatim are designed to walk a line between being portable and comfortable platforms. In terms of mice, I'm a fan of large platforms that support my wrist with adequate height, so carrying one around has been out of the question. Because I use a Mac, I've found that the trackpad is more than adequate in terms of gestured input and overall feel. Until now, I had never seriously used a portable laptop mouse as some of my colleagues do. We'll see if I can be convinced to carry one with me!