I was happy with the company that hosted my sites before I switched to DreamHost, but the lure of more space tempted me to sign with DH.
DreamHost has a lot of great features. I'm happy about that. But I'm greatly disappointed with the decrease of my sites' speed since I copied my files and databases over to one of DreamHost's shared servers.
I run TYPO3, which is quite hungry for server resources, but then again, my sites have no problem running fast on other bargain priced shared hosting providers.
Word around the web seems to say that database driven applications may experience some latency due to some characteristics of DreamHosts network.
Some have hinted that running eaccellerator or using php in fast-cgi mode would help. I've tested both of those options to no avail.
My site crawls on DreamHost and I'd like to read any performance increasing suggestions other customers may have.