I finally moved onto a VPS and I've got to say that W3TC really makes it fly now when caching everything in APC, which I couldn't do on shared hosting. Webpagetest.org shows ~.530 sec full page load times! This is using the Thematic theme, WP 3.2.1, nginx, and W3TC to cache everything in APC. Truly 'snappy'. It actually feels as responsive now as I've been trying to make it feel for ages.
Only issue though, is that the minified CSS URL is incorrect and not working. It's adding the /wordpress directory, in which WordPress is installed, into the minified CSS URL. I've looked through inc/define.php and /lib/W3/Plugin/Minify.php, but just can't seem to find what might be causing it.
It's creating this CSS link URL (which 404's & leaves the site unstyled):
But should be creating:
('Site' is my wp-content directory as defined in wp-config.php, and sits outside of /wordpress, in the root. This way if I ever have issues with wordpress, I've been able to trash the entire directory, reupload and I'm good to go. And I don't risk accidentally deleting my content ever that way. The plugins directory has not been renamed, since I remember that isn't compatible with W3TC yet.)