We have been trying to get our Word Press pages to load as fast as you would expect them to. We eventually went to 'Really Static' to cache our web pages. It knocked the socks off of every other WP cache program! Then we upgraded to WP 3.0 and our site speed dropped back to what it was before we used a caching program.
Another feature to change in WP Super Cache from the default settings is to enable 'preload cache mode' and set the time to 1440 minutes. That is to only load the cache every 24 hours. That is fine for us because we do not allow comments, you would have to make an exception for comments if you allow comments.
All together though it appears like WP 3.0 is REALLY SLOW! We are trying to find a solution, but let me know if you know of one!