I wouldn't attempt to run "anything of any importance" on a VPS, particularly when dedicated is so cheap these days for basic boxes.
I run a VPS for development sites only with Poundhost, the box is OK; there was a period of downtime a while back which lasted a couple of days [at the weekend] thanks to the failure of the shared HP disk drive unit (the name of the thing evades me at the moment) however the current offering appears to be SAS storage:
http://vds.poundhost.com/template.aspx?ID=4
It's fine for development, but I wouldn't put any production sites on it or indeed any VPS.