Oh, forgot to point out the other big difference. Slicehost had (and still has) a monthly billing model with a monthly bandwidth allowance bundled into the cost. Rackspace Cloud Servers costs are calculated on two factors: how many hours the Cloud Server ran that month (from the day/time you instantiated it); AND then bandwidth usage is calculated separately, based on some $$/GB rate:

http://www.rackspace.com/cloud/cloud_hosting_products/server...

So, the real point is that even if this wasn't apparent to you the customer, the substantial differences between Cloud Servers and Slices was branding and different pricing models; the support teams were also separate (and the two front-line support teams have different "styles"). Otherwise, behind the scenes, they're literally the same thing -- in terms of data centers, hardware platforms and hypervisors, etc., etc.