Agreed with all of this- to date, I've bought a 7d, 50 1.4, and 2 430ex IIs. Most of them during sales, and they've been indistinguishable from new every time. Once I save up some money, my "go full-frame" plan is to buy a refurb 5d3 with canon loyalty program discount (have an old P&S to use for this), and 24-70 if I can get a discount on that too.
(Canon Loyalty Program makes every day your birthday- trade in an old body (doesn't have to be functional, or remotely new. Could be P&S or film SLR), get a discount on a refurb body, sometimes lenses from what I hear.)