(http://img.neoseeker.com/n/7/win739214d3ac4c64bfbb229ce607261feef_thumb.png)
For those really looking to give back, beyond just using the Windows 7 release candidate and automatically sending data to Microsoft, there's a program being put off called Windows 7 Scenario Feedback. Just head over to the website linked below, enter your information, and have at 'er.
The questions regard what you'd expect -- things like quality, when you plan to install, etc. and come in a yes/no and scale of 1-7 format. Easy stuff.
The RC's been about for about two weeks now, so it should prove a good amount of time to have formulated your collective impressions and then send them off, if that's what you're into.
You can do it here;
http://input.microsoft.com/scenarios/preferences.aspx?&Site=f70b487a-3961-496d-8f29-bc96b1726b19&csg=7a7648b0-0d83-4ca5-be66-3b85220c32ae&category=0