I have no responses from other DH customers. I've done a LOT of research on performance tuning at various sites specializing in Drupal, MySQL, Apache, and PHP. My head is swimming with details about what should be done to test and tune each component of the environment vs what can be done in a shared-host environment. A lot of info about tuning is old, for D4 or D5, maybe MySQL 4. Then there are conflicting details like "load the devel module and run X to find bottlenecks", but the devel module for D6 currently has a lot of open support issues for runaway processes and issues that may get flagged on a DH server as a resource hog. I don't want to get my site locked out for resource abuse just because I want to find out why it's slow. Such are the pains of working on a shared host. Can I move to a private server? Sure but I read in these forums the waiting line is a couple months long and I don't have that sort of time and I don't want to incur that expense just for a testing environment.
Dreamhost is fairly well recognized in the Drupal community as a common Drupal hosting environment but unfortunately among other such hosts the impression I get is that people like DH in general but it's one of the slowest hosts around. Now remember, I didn't come at this with any prior knowledge or bias, this is what I'm getting from other people's comments so arguments with me to the contrary are futile.
So my latest thinking is that it's fine to host my company apps here (Wordpress, Mantis, SmartMachinesForum, couple other small ones) but if I expect the site to grow with a reasonable number of hits I'll need a private host and may need to go with a company other than DH. This pains me and it would be easily avoidable if we could find a "champion" at DH who can offer DH-specific tuning tips with a focus on Drupal.
My current goal is to do as much as I can here as far as familiarizing with modules, where performance doesn't matter. I'll setup a LAMP environment here in my office with software releases similar to DH. I'll do my best to get benchmarks on various specific activities. I'll try to tune this environment as best as I can. Then I'll take my numbers, do what I can at DH or other hosts and see where I can get the best numbers.
When I first came to DH I thought we would be seeing more participation from the crew over there in terms of helping sites to get the most out of the environment, but I've come to realize that all we have here are our fellow customers, all trying to approach the black box as best we can without much help from inside. If anyone else has a better way to engage DH in activities like this, I'm all ears. I'm feeling very alone at the moment, need to do a ton of research on my own, and feeling compelled to take "real" business elsewhere if only to find another black box host that just runs faster. Again, this is an easy problem to remedy, but I don't know how to get more from DH on this except to file a normal Support ticket, and that's not the way I want to do this.
More will follow later as I assimilate the info. I might update the DH wiki with a major list of D6 resources for performance tuning but first I want to narrow it down to quality rather than quantity.