W3 Total Cache (W3TC) is a great caching plugin. Using it on my modest server (512MB VM from Rackspace) I've seen both a dramatic decreased in page load times as well as reduced server load. However, it can be a chore to get it working correctly, I've had issues with the Rackspace CDN integration. Fortunately their support is top-notch and the developer listens to you when you submit a bug.
I like to play with the inter-workings of awaitinginspiration.com, which sometimes means that I break things and then have to fix them. I was messing around with the permalinks on the site a few days ago and didn't notice that as a result I broke several posts, including my original iPhone Call Recorder post (the single most popular post on the site). The issue seemed to be somewhat sporadic, sometimes a problematic post would show correctly, and sometimes you'd get a message saying that the post could not be found. I was not sure what was going on. Eventually, like just about an hour ago, it occurred to my that the issue may stem from my permalink hi-jinks the other day and the W3 Total Cache plugin. Sure enough, it as a simple as clearing all the W3TC caches. Once the caches were cleared posts came up without an issue. So, the takeaway - if you use a caching plugin/system and make changes to your site; clear your cache.