Even as a NW Silver, the upgrades are relatively plentiful on everything but packed flights. And yes, for me at least, they are one of the biggest reasons I'm a WP member - I haven't yet booked any award travel.

It's for good reason I have an interest in the upgrades, as my company (and I know many others are in the same boat here) absolutely prohibits us from purchasing anything other than economy tickets. And going through corporate travel we have no real way to pick what fare class we're in, so I often am in discounted economy. So in the interest of getting the most comfort out of domestic flights, WP has been great to me.