Power
Backing up the MacBook's hardware and software capabilities is a power source that keeps on going. Typical battery performance ranges from 6-10 hours, which makes a full-workday possible on a single charge. It's liberating to pick up my MacBook and go to a meeting or lunch without lugging around extension cords. If there is a downside to the MacBook battery, it's the lack of user serviceability. However, the battery can be replaced for $130-$180 at any Apple store if they stop holding a charge. This cost compares favorably to traditional battery replacements on older MacBooks, but does necessitate a Genius Bar appointment.
Support
The final, and probably best, reason to be excited about the MacBook is supportnot Apple support, but support from the developer community. The Macintosh has changed from the "oddball" computer with little software support to a strong, vibrant platform. Traditionally weak areas, such as gaming, have taken off. In mid-May 2010, for example, Valve software is releasing the "Steam" gaming platform for Mac OS X. Steam is arguably the most popular gaming platform for Windows, providing on-demand games with only a few clicks. Bringing this option to the MacBook makes it a mobile gaming platform that can hold its own with Windows.
The Sum of Its Parts
With these strides in performance, video handling, battery life, and the resulting developer appeal, the MacBook has truly come of age. Using one no longer feels like a compromise between portability and performance. The CPU, graphics processor, and dozens of other improvements under the hood create a user experience that is more responsive, more efficient, more productive, and ultimately more enjoyable. Of course, there will always be something newer and better just around the corner, but my personal hesitation about choosing a MacBook as my primary platform is gone and my desktop machines are gathering dust.