WP-Cache, what does it do?

A very powerful plugin for WordPress, WP-Cache is a systematic caching system that aims to improve the overall performance of WordPress while still providing many options for configuring the caching itself. Its main purpose is to reduce server load in extreme conditions, like that of a Digging.

The Options

The most important part of WP-Cache is its string matching system that allows you to specify what pages should and shouldn't be cached by simply including their URL. You can also specify an expire time for cached pages, and can quickly delete all cached and expired pages to reduce file size on the server.

Performance?

I have not personally been able to run some absolute performance testing, and on a server like the MediaTemple (gs) GridServer, it is unlikely that I will be using it for a long time. None the less, WP-Cache is a very powerful plugin that should come in handy for surviving any traffic spike.

Are the stories true?

I've heard my share of horror stories about WordPress blogs crashing under moderate diggings because of under-optimized themes. Since I'm on a GridServer right now that doesn't have me worried much, but if my blog actually becomes somewhat popular (Yeah, right!) and starts using up a lot of resources I might actually have to worry about theme optimization. Have any of you been forced to optimize your own themes to deal with server load?