I installed WP Super Cache on this blog as a drop-in replacement for WP-Cache (which I disabled because of compatibility issues with PHP5). After enabling WP Super Cache and turning on the Super Cache Compression option, I can see a huge improvement in page load times. A page I always use for testing is the Archives page, which normally executes almost 2,000 SQL queries. Without the cache plugin, that page took almost 5 seconds to load. Now it loads in less than 2 seconds.