The way this integrates is clean, but I'm not certain what nopt does that optimist doesn't.

What about nopt sold you?

Other than "I was already using it, and don't want to migrate to optimist":

• Specifying parameters that are always Arrays, even with a single value: { "stuff": [path, Array] }
• Specifying parameters of an explicit type, or array of types, with the first success determining the choice: { "stringOrDate": [Date, String] }
• Shorthands that expand to composite longhands: { "s": ["--stuff", "--things", "foo"] }

Also, as @isaacs noted, type verification and custom parsing capabilities.

After much reflection (noting the way that nopt parses options when using npm, and asking myself what would it be like with optimist?) I have decided to merge this.

merged into rc@0.2.0

Thanks!