Simply invaluable. Worth every cent.

You may wonder why you would ever need this given that the entire internet is at your fingertips. Try writing code in a 16-hour international flight (without paying extortion money for GoGo in-flight wifi), or debugging something when the ISP or your IT department is having a "service outage". Its also much much faster than waiting on websites to load and hoping your Google search is specific enough to give you properly-constrained results.

Plus a companion iOS app.

Dash is so awesome.

brysonholland about Dash 3 - API Docs & Snippets. Integrates with Xcode, Alfred, TextWrangler and many more.