You have four things that I can note :

• You are passing an input in the root component, which will not work.
• As @alexpods mentioned, you are using CamelCase. You should not.
• You are passing an expression instead of an string through [test]. That means that angular2 is looking for a variable named Blue32 instead of passing a raw string.
• You are using the constructor. That will not work, it must be after the view has been initialized data-bound properties have been initialized (see docs for OnInit).

So with a few fixes it should work

Example updated to beta 1

import {Component, Input} from 'angular2/core';
import {bootstrap} from 'angular2/platform/browser';

@Component({
  selector : 'childcmp',
  template: `Test Value : {{test}}`
})
class ChildCmp {
    @Input() test: string;
    ngOnInit() {
        console.log('This if the value for user-id: ' + this.test);
    }
}

@Component({
    selector: 'testcmp',
    template : `<childcmp [test]="'Blue32'"></childcmp>`
    directives : [ChildCmp]
})
export class TestCmp {}

bootstrap(TestCmp);

See this plnkr as an example.

Update

I see that people still reach this answer, so I’ve updated the plnkr to beta 1 and I corrected one point on the explanation : You can access inputs in ngAfterViewInit, but you can access them earlier in the lifecycle within ngOnInit.