Given the anecdotal evidence as well as surveys, it seem you've just been lucky (as was I for numerous years till this year). My recent support experience was terribly frustrating until I did two things: asked to be routed to retention, and then filed a form to email their VP: http://customer.xfinity.com/help-and-support/vp-contact-form

Speed issues still aren't resolved, but it's tolerable now.