If you’re expecting to get slashdotted or digged or otherwise want more performance out of your WordPress installation, you might try this:
http://mnm.uib.es/gallir/wp-cache-2/
I actually tried it for a few minutes and I didn’t notice a speed increase worth the trouble of not seeing my updates right away. YMMV.
I was using wp-cache (2 I think) for a while, but found it more of a pain than anything. Page loads still hit the database, which at dreamhost is at least a hop away. Overall I only saw a 20% improvement.
My best page load improvements came from 2 things: optimising my WordPress theme (reducing db hits, and farming content to other subdomains), and Dreamhost’s general routing improvements this summer.
FWIW, yesterday’s digg/reddit flood on my site seemed to barely phase my shared Dreamhost box (5-10k hits per hour, for 15 hours, page load times were fairly constant at .5-2s).