Too bad they didn't match Linode's offerings. http://www.linode.com/
Comparison between Slicehost, Linode, Prgmr, Rackspace, Amazon: http://journal.uggedal.com/vps-performance-comparison
Personal experience: Linode move from a linode 360 to a linode 540 took under 15 minutes from time submitting support ticket to resizing and rebooting, pro rating pricing is very awesome
The pricing isn't so good, though.
Linode eventually sold me on their new datacenter in London.