I use me... but then that's because I'm affiliated with the organization that I run Fusion for and also host their 3 sites. So hosting Fusion is no problem and we have all the goodies like the best ant-spam/anti-virus available, firewall/long-since cPanel 11, choice of PHP 4 or 5, and mainly no overselling period.
But I am no coder so I do not offer Fusion or any other "3rd party" specific support and because of my disabilities I prefer "low maintenance" customers who don't need rapid support at 3 am etc.
But we can handle Fusion's demands easily (it's really coded well so it's easy on the servers) and also if you know anyone who needs a great DIY site builder we offer the best on the market as a freebie.
I'm definitely a "niche" guy (no 24/7 fast support and I as I said I don't offer 3rd party support even for Fusion but I keep good equipment/latest software/high uptime and uncrowded boxes on fast ports from Equinix in Chicago so you can e-mail if you have questions and just need a basic, solid, host. (No shell access-security comes first)
PS: By latest I don't mean "bleeding edge" but soon I'll fire up a box with Apache 2 and the latest MySQL so I can start seeing the things I'll need to be working on for when they become the standard instead of just the newest.
(and Josh if this is inappropriate just delete it, didn't see it in the rules but don't mean to violate anything)