Scenario: 

You have a Feature that attaches an event receiver to a given content type.  That content type is created and syndicated via SharePoint 2010's content type hub.  You want to understand the process for deploying or updating it across subscribing site collections.

Deployment Procedure:

1. Deploy event receiver feature to farm (add solution, deploy solution)

2. Active feature on Content Type Hub site.

3. Modify the publishing status of the content type which your event receiver is attached to.  Publish or Re-publish the content type.  Do not run the Content Type Hub job or the Content Type Subscriber jobs yet.  If they are running within a very short interval turn down the frequency to every 30 minutes (important!).

4. Activate the feature on all the subscribing site collections.

5. Run the content type hub timer job.  Wait until the job finishes.  Run the content type subscriber job for all the web applications where this feature will live.

6. Open your subscribing site collections in SharePoint Manager (SPM on CodePlex).  Verify that in each library where your content type lives you see the event receiver attached.

Pre-pare for Update / Removal Procedure:

1. Go the Content Type Hub Site.  De-activate Feature.

2. Update Publishing Status for Content Types.

3. Run content type hub and subscriber jobs.

4. De-activate Feature on subscriber sites.

5. Retract solution.

6. Remove Solution.

7. Check libraries with SPM to ensure that Event Receiver has been removed.

8. Delete manually if not removed.

9. If updating repeat previous steps for installation / deployment.

Good luck!