The interesting thing is that linode started out as a cheaper alternative to slicehost, so its ironic that they are now trying to differentiate themselves in much the same way slicehost did back then.
You have that backwards, given that Linode predated Slicehost by upwards of three years.
Linode have been around since 2003. I think Slicehost was founded later than this (in 2006 according to a quick search for their name.)
This is correct. I signed up with Linode in 2005 and there was no Slicehost then. I was moving from another VPS provider (Redwood Virtual) which had twice the resources for the same price as Linode but were really, really crummy (they don't even exist anymore). That experience really taught me the value of considering quality in addition to the price/feature ratio, which is why I'm not jumping ship to DigitalOcean. (I might if/when they establish a solid reputation, but no sooner.)