There appears to be a problem - not caused by SPFX when following the instructions -> https://dev.office.com/sharepoint/docs/spfx/web-parts/get-started/build-a-hello-world-web-part now that RC0 has been released.
This causes a problem when you enter gulp serve .
Error - typescript - node_modules\@types\lodash\index.d.ts(245,25): error TS2304: Cannot find name 'Partial' .
This error is caused by this issue -> https://github.com/DefinitelyTyped/DefinitelyTyped/pull/13994 which is nothing to do with SPFX.
The fix is to do this :- npm install @types/lodash@4.14.50
