I'm using Slicehost, and it's been a really great experience. I've been with them for about a year, and haven't had any downtime that I've noticed. Current uptime is 82 days, and that was when I changed over from Ubuntu to Debian.
I've also tried a Joyent accelerator, and wasn't very happy with it.
I've also tried a Joyent accelerator, and wasn't very happy with it.