Well, I do not switch because my slice keeps being online and available for almost two years now. "Never change a running system" ;).

I do, however, also have a Linode VPS and will probably go with additional Linode VPS' in the future if the service continues to be stable.

In my humble opinion, Slicehost offered a great deal two years ago but they should adjust their plans in the future or customers will move to competitors.