Dashboard isn't for everyone. And if you're undecided if you're one of them, DashPrefs makes it easy for you to keep making this choice, whenever you want. Even right now! With DashPrefs, you can:
Disable Dashboard entirely - without rebooting, without anything. Saves you system resources, and it doesn't get in your way in the worst moment!
Disable Dashboard's Advisory feature. This was introduced in 10.4.7, and permanently checks every 8 hours whether your widgets match those at apple.com - otherwise, an intruder could put malicious widgets on your computer, which otherwise would be virtually indistinguishable, if even at all noticeable. Apparently a useful feature, but unfortunately very vaguely documented by Apple, who don't provide options for it, let alone a user-friendly means of turning it off!
What's new in DashPrefs
Added Japanese translation. Thanks Yuzuru 'E-WA' Shiraiwa!